J.  Milter t 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


Ik  RALPH  D.  i£EB  LffiRAKY 

0£»'A*TMENT  OF  GEOLOGY 

UNIVERSITY  of  CALIFORNIA 

'  0  <  ANiiJ-XES.  CALIF. 


Shtff 


PRACTICAL  EXERCISES  IN 
PHYSICAL  GEOGRAPHY 


BY 

WILLIAM  MORRIS  DAVIS 

PROFESSOR  OF  GEOLOGY  IN  HARVARD  UNIVERSITY 


GINN  &  COMPANY 

BOSTON  •  NEW  YORK  •  CHICAGO  •  LONDON 


COPYRIGHT,  1908,  BY 
WILLIAM  MOREIS  DAVIS 


ALL  RIGHTS   RESERVED 
88.5 


Cfte   gtfctnaum   ffrtfl* 

GINN    &   COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


Library 


PREFACE 


The  object  of  this  Text  and  the  accompanying  Atlas  is  to  provide 
in  as  compact  a  form  as  possible  a  series  of  disciplinary  exercises 
which  may  be  assigned  as  "  laboratory  work  "  in  connection  with  any 
of  the  modern  text-books  on  Physical  Geography. 

The  need  of  such  exercises  is  generally  recognized.  Experience 
has  shown  that  a  student  may  fail  to  acquire  a  clear  understand- 
ing of  the  facts  and  problems  of  Physical  Geography  if  they  are 
presented  only  through  the  text  of  a  printed  page ;  and  that  even 
the  ornamentation  of  the  page  by  pertinent  illustrations  does  not 
always  suffice  to  ensure  a  full  comprehension  of  essential  points. 
The  student's  attention  must  be  directed  to  and  detained  upon  each 
feature  of  a  complicated  fact,  each  step  of  a  large  problem,  in  order 
that  the  facts  and  problems  may  reach  his  understanding  and  remain 
in  his  memory  ;  hence  the  desirability  of  combining  the  performance 
of  a  series  of  systematic  exercises  with  the  study  of  a  text. 

The  topics  selected  for  the  Exercises  here  presented  are  such  as 
are  treated  in  greater  or  less  fullness  in  all  modern  text-books.  The 
Exercises  may  be  taken  up  in  such  order  as  the  teacher  shall  deter- 
mine :  those  on  the  atmosphere  and  the  ocean  may  follow  or  precede 
those  on  the  lands ;  those  on  the  lands  may  be  rearranged  if  desired, 
except  that  it  is  well  to  place  Exercise  I  early  in  the  series  because 
of  its  many  applications,  and  to  place  Exercises  VII  and  VIII  late 
in  the  series  because  of  the  greater  detail  of  their  problems. 

The  method  recommended  for  performing  the  Exercises  is  stated 
in  the  General  Instructions  (pp.  1  and  2).  It  may  be  here  added 
that  it  will  be  found  useful  to  allow  students  to  read  the  Text  and 
to  examine  the  Atlas  in  a  preliminary  study  period,  and  thus  to 


754289 


iv  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

construct  mental  answers  and  imaginary  diagrams  in  preparation 
for  oral  answers  in  a  recitation  or  for  written  and  graphic  answers 
in  a  laboratory  period. 

The  Exercises  are  not  divided  into  separate  lessons ;  they  are  left 
like  the  chapters  of  a  text-book,  to  be  divided  by  the  teacher  accord- 
ing to  the  time  assigned  for  laboratory  work  and  to  the  advance- 
ment of  the  pupils.  The  Exercises  are,  moreover,  planned  so  that 
they  may  be  used  for  a  shorter  or  a  longer  course,  according  to  the 
time  allotted  to  Physical  Geography  in  a  programme  of  studies. 
In  a  short  course  all  the  bracketed  questions  and  sections  may  be 
omitted  without  lessening  the  continuity  of  the  work.  For  still  more 
abbreviation,  written  answers  in  the  pupil's  notebook  may  be  replaced 
by  oral  answers  recited  in  succession  by  different  members  of  a  class  ; 
but  it  is  recommended  that  after  such  a  recitation  the  teacher  should 
indicate  certain  questions  for  which  the  answers  should  be  carefully 
written  by  all  members  of  the  class  in  order  to  secure  a  clear  under- 
standing of  the  most  important  points. 

The  Exercises  may  be  profitably  extended  through  a  longer  course 
by  requiring  written  answers,  carefully  phrased,  for  all  questions 
in  the  Text.  Additional  questions,  which  every  teacher  will  inevi- 
tably invent  for  himself  as  the  work  progresses,  may  be  frequently 
introduced.  Questions  concerning  opportunity  for  human  settle- 
ment and  movement,  conditions  of  human  occupations,  etc.,  may 
be  greatly  increased.  Some  examples  of  such  questions  are  given, 
as  in  Exercise  V,  §  §  3  and  12 ;  but  it  has  been  necessary  to  exclude 
them,  as  a  rule,  in  order  to  save  space.  Still  further  extension  of  a 
very  profitable  kind  may  be  made  by  having  the  pupil  draw  temper- 
ature and  pressure  gradients  and  generalize  wind  movements  on 
selected  governmental  weather  maps,  following  the  methods  of  Exer- 
cise XII ;  or  by  calling  for  the  preparation  of  maps,  in  hachures  or 
contours,  of  selected  parts  of  the  land  forms  shown  in  the  block 
diagrams  of  the  Atlas  ;  or  by  assigning  certain  parts  of  selected 
topographical  maps  published  by  governmental  surveys  for  careful 
description  and  explanation.  But  in  all  cases,  whether  the  work 


PREFACE  v 

makes  part  of  a  long  or  of  a  short  course,  it  is  advised  that  minute 
accuracy  is  not  to  be  expected  in  the  answers  to  questions  regarding 
distances,  altitudes,  and  locations,  and  that,  in  general,  the  answers 
to  questions  should  be  simple  rather  than  elaborate. 

The  plates  in  the  Atlas  on  which  the  Exercises  are  largely  based 
are  in  most  cases  ideal  designs  and  not  copies  of  actual  occurrences  ; 
but  the  charts  of  mean  temperatures,  prevailing  winds,  and  ocean 
currents  are  exceptions  to  this  statement.  The  reason  for  giving 
ideal  examples  of  weather  maps  and  of  land  forms  is,  that  only  in 
this  way  can  the  systematic  progress  of  teaching  be  secured.  In 
the  daily  weather  maps  and  on  the  large-scale  topographical  maps 
published  by  our  governmental  bureaus,  the  illustrations  of  typical 
features  are  nearly  always  complicated  by  the  addition  of  irrele- 
vant details,  which  are  distracting  to  the  beginner.  Moreover,  these 
official  maps  do  not  and  should  not  attempt  to  emphasize  certain 
typical  features  and  to  subordinate  unessential  details ;  they  are 
prepared  for  adult  experts  ;  they  must  present  the  facts  of  nature 
in  all  the  complications  of  their  actual  occurrence.  But  to  use  such 
maps  in  the  first  lessons  on  Physical  Geography  would  be  much  the 
same  as  to  use  pages  of  actual  accounts  taken  from  the  books  of  a 
large  commercial  establishment  in  the  first  lessons  in  arithmetic, 
and  thus  to  introduce  division,  interest,  addition,  fractions,  and  so 
on,  in  the  haphazard  order  of  their  daily  occurrence  in  business, 
instead  of  in  a  well-arranged,  systematic  order  appropriate  for  a 
beginner's  study  in  school. 

The  author  is,  however,  aware  of  various  imperfections  in  the 
ideal  diagrams  of  the  Atlas.  Effort  was  made  to  find  a  professional 
draftsman  who  would  prepare  thoroughly  satisfactory  drawings,  but 
no  one  could  be  discovered  who  possessed  at  once  a  sufficient  knowl- 
edge of  the  subject  and  a  trained  proficiency  of  handiwork.  Among 
the  shortcomings  which  a  redrawing  might  lessen  are  certain  errors 
of  perspective  in  some  of  the  block  diagrams ;  some  unintentional 
disagreement  of  scales  among  the  successive  members  of  a  single 
series  of  diagrams ;  an  insufficient  depth  in  the  gorge  between  lakes 


vi  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

A  and  C,  in  17  2  (for  manner  of  reference  to  Plates  and  Figures  see 
p.  1),  and  a  lack  of  expressive  emphasis  in  the  shading  of  the  sea 
cliffs  in  35  1.  It  is  hoped  that  these  subordinate  defects  will  not 
seriously  interfere  with  the  usefulness  of  the  diagrams  for  the  pur- 
poses of  teaching. 

The  importance  of  associating  actual  phenomena,  as  they  occur 
in  nature,  with  the  ideal  types  given  in  the  Atlas  is  fully  recognized. 
A  step  towards  such  association  is  made  by  introducing  in  Plates 
35-39  a  number  of  maps,  reproduced  with  more  or  less  simplification 
from  parts  of  selected  topographical  sheets  of  different  areas  in  the 
United  States,  published  by  the  National  Geological  Survey  (see 
explanation  of  plates,  page  3  of  Atlas),  and  by  calling  for  the  location 
of  these  actual  examples,  as  well  as  of  a  number  of  other  examples 
indicated  by  name  in  the  Text,  on  the  outline  maps  of  the  United 
States  and  the  continents,  Plates  40-45.  All  these  actual  examples 
should  be  carefully  learned  by  name  and  location  in  order  to  give 
reality  to  the  Exercises.  Just  as  the  condensed  statements  of  a 
text-book  should  be  elaborated  by  the  teacher  and  illustrated  by  the 
exhibition  of  appropriate  maps,  pictures,  and  specimens,  so  this 
Text  and  its  Atlas  may  be  profitably  supplemented  by  the  exhi- 
bition of  selected  weather  maps,  published  by  the  Weather  Bureau, 
Department  of  Agriculture ;  by  the  study  of  full-sized  topographical 
maps  published  by  various  governmental  bureaus  ;  and  by  the  exami- 
nation of  such  photographs  and  lantern  slides  as  may  be  available  to 
illustrate  the  problems  in  hand.  If  experimental  illustrations  of  the 
formation  of  valleys,  deltas,  shore  cliffs,  volcanoes,  etc.,  can  be  given 
in  what  has  been  called  the  "  wet  laboratory,"  following  the  sugges- 
tions that  have  recently  been  made  by  some  expert  teachers,  so  much 
the  better. 

Field  excursions  are  also  to  be  strongly  recommended  as  a  means 
of  giving  reality  to  problems  that  might  otherwise  be  regarded  as 
abstractions.  It  is  particularly  urged  that  the  Exercises  here  pre- 
sented should  not  be  taken  to  replace  field  excursions ;  but  rather 
that  the  principles  illustrated  in  the  Exercises  should,  as  far  as 


PREFACE  vii 

possible,  be  given  additional  illustration  by  systematic  excursions  in 
the  school  district.  It  is  in  connection  with  such  excursions  that 
the  teacher  may  to  best  advantage  first  teach  something  of  different 
kinds  of  rocks,  taken  from  their  actual  outcrops  and  selected  to 
illustrate  varying  degrees  of  resistance  to  weathering.  Alluvial 
deposits  of  gravel,  sand,  and  clay  should  also  be  examined  in  field 
study.  Similarly,  local  weather  observations  should  be  undertaken 
for  the  determination  of  temperatures,  wind  directions,  changes 
from  clear  to  cloudy  sky,  rainfall,  and  so  on.  It  will  be  of  decided 
advantage  if  the  chief  facts  concerning  the  sun's  seasonal  change 
of  altitude  and  the  associated  changes  in  the  points  of  sunrise  and 
sunset,  and  of  the  length  of  day  and  night,  can  be  introduced  in  an 
earlier  year  than  the  one  in  which  these  Exercises  are  studied.  If 
this  is  not  conveniently  possible,  then  the  most  important  observa- 
tions on  the  sun,  as  referred  to  in  Exercise  X,  §§  4,  5,  should  be 
made  while  the  Exercises  on  land  forms  are  studied ;  and  the  Exer- 
cises on  the  atmosphere  should  come  near  the  close  of  the  year. 

It  would  truly  be  vastly  better  if,  in  the  study  of  land  forms, 
actvial  examples  of  all  typical  features  could  be  made  the  subject 
of  systematic  observation  and  description  in  the  field  by  every 
pupil,  and  if  in  the  study  of  the  temperatures,  winds,  and  ocean  cur- 
rents of  different  parts  of  the  world,  the  class  could  visit  the  regions 
where  the  actual  phenomena  are  observable ;  but  this  is  manifestly 
impossible.  Even  the  most  favored  school  district  does  not  include 
a  complete  and  well-ordered  series  of  all  the  different  kinds  of  land 
forms  which  every  student  of  Physical  Geography  should  learn  to 
know ;  indeed,  such  forms  as  it  includes  are  often  imperfect  or  com- 
plicated examples  of  their  kind,  and  it  is  not  always  possible  for  a 
class  to  visit  them  on  the  day  and  hour  when  they  are  reached  in  the 
regular  progress  of  class  work.  Hence  the  necessity  of  presenting 
the  facts  of  our  science  largely  through  descriptions  and  imitative 
illustrations.  Nevertheless,  so  great  is  the  power  of  the  construct- 
ive imagination  on  the  part  of  young  students  that  no  serious 
difficulty  should  be  found  in  giving  sufficient  reality  to  the  charts 


viii  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

of  temperatures,  winds,  and  currents,  which  graphically  represent 
average  values  of  observed  phenomena  in  Exercises  X,  XI,  and 
XIII ;  or  to  block  diagrams  such  as  illustrate  the  series  of  volcanic 
forms  in  Exercise  VI ;  or  to  maps  such  as  illustrate  the  series  of 
shore-line  forms  in  Exercise  IX. 

It  is  believed  that  great  progress  can  be  made  when  imitative 
ideal  illustrations  are  used  as  the  basis  of  practical  work  under  the 
direction  of  a  good  teacher  and  in  association  with  an  appropriate 
text-book.  It  goes  without  saying  that,  as  already  noted  above,  sup- 
plementary illustrations  are  useful  and  helpful ;  but  the  effort  has 
been  made  to  provide  so  much  of  the  essential  material  in  this 
Text  and  its  Atlas  that  the  labor  of  the  teacher  in  supplementing 
it  shall  be  as  light  as  possible.  The  careful  performance  of  the 
Exercises  will  lead  the  pxipil  to  observe,  to  describe,  and  to  general- 
ize ;  to  make  inferences,  to  invent  explanations,  and  to  test  theories ; 
to  express  new  ideas  verbally  and  graphically.  If  the  teacher  is 
patient  and  does  not  infringe  too  often  on  the  pupil's  right  of  dis- 
covery, the  pupil  may  make  so  much  progress  in  these  various 
processes,  and  at  the  same  time  acquire  so  good  a  knowledge  of  a 
great  group  of  natural  phenomena,  that  he  will  really  be  led  to 
make  a  beginning  in  the  formation  of  scientific  habits  of  thought. 

The  value  of  practical  exercises  in  association  with  text-book 
lessons  may  be  illustrated  by  comparing  the  impression  made  upon 
a  student  by  the  study  of  the  important  generalization,  found  ready- 
made  on  a  printed  page,  concerning  the  slopes  of  rivers  and  the 
accordant  junctions  of  branch  and  main  streams,  with  the  impres- 
sion made  upon  him  by  having  to  develop  the  generalization  himself 
on  the  basis  of  a  diagram  of  river  profiles  that  he  has  constructed 
with  his  own  hands,  as  in  Exercise  I,  §  4.  There  can  be  little  ques- 
tion that  the  reality  of  the  facts  involved,  and  the  truth  of  the 
generalization  that  represents  the  relations  of  the  facts,  are  best 
apprehended  through  practical  exercises ;  but  at  the  same  time  it 
may  well  be  that  the  wording  of  the  generalization  is  not  so  clearly 
given  in  the  student's  notebook  as  in  the  text-book,  where  it  should 


PREFACE  ix 

therefore  be  carefully  learned.  Again,  compare  the  strength  of  con- 
viction regarding  the  features  and  relations  of  antecedent  rivers, 
according  as  they  are  studied  in  the  paragraph  of  a  text-book  or 
worked  out  by  some  such  method  as  is  offered  in  Exercise  V,  §  8 ; 
yet  the  paragraph  in  the  text-book  is  a  valuable  supplement  to  the 
results  of  the  practical  exercise.  Compare  the  clearness  and  fullness 
of  conception  of  the  phenomena  of  river  capture  and  the  associated 
features,  according  as  they  are  learned  in  a  text-book  or  worked  out 
by  means  of  illustrative  diagrams  showing  the  successive  stages  of 
the  processes  involved,  in  some  such  way  as  is  suggested  in  Exer- 
cise IX,  §  §  4,  5,  6.  Furthermore,  the  value  of  the  careful  analysis 
of  a  problem  and  of  the  successive  presentation  of  its  parts  in 
systematically  arranged  diagrams  is  illustrated  in  Exercise  XII. 
There  can  be  little  question  that  such  weather  maps  as  those  of 
Plate  33,  even  though  they  are  only  ideal  diagrams,  will  introduce 
the  problem  of  weather  changes  much  better  than  can  be  done  by 
basing  the  work  immediately  on  governmental  weather  maps. 

Large  generalizations  must  be  given  abundant  and  repeated  oppor- 
tunity to  establish  themselves  in  the  mind.  It  is  for  this  reason 
that  so  many  returns  are  made  in  Exercises  I-IX  to  the  problem 
of  the  Geographical  Cycle  and  to  the  systematic  succession  in  the 
development  of  land  forms  that  it  embodies.  The  explanatory 
method  that  has  long  been  employed  in  the  study  of  the  air  and 
the  oceans  is  here  introduced  in  the  treatment  of  the  lands  as  well, 
where  its  thoroughgoing  application  constitutes  the  greatest  advance 
made  in  Physical  Geography  in  the  last  century.  But  it  is  important 
to  remember  that  in  all  cases  where  land  forms  are  described  in 
terms  of  the  processes  involved  in  producing  them,  the  attention  of 
the  geographer  should  be  held  primarily  to  the  forms  thus  produced, 
and  given  only  secondarily  to  the  processes  to  which  they  are  due. 
The  systematic  advance  in  the  development  of  these  forms,  involved 
in  the  scheme  of  the  Geographical  Cycle,  has  in  recent  years  sug- 
gested the  use  of  such  terms  as  young,  mature,  and  old.  The 
scheme  of  the  Cycle  once  being  known,  a  valley  and  its  stream  may 


x  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

be  described  as  "  young " ;  and  the  student  is  thereby  most  easily 
led  to  apprehend  all  the  characteristic  features  of  the  valley  in 
their  natural  occurrence.  A  group  of  mountains  may  be  described 
as  approaching  old  age,  and  thus  their  essential  features  are  most 
easily  brought  to  mind.  A  shore  line  may  be  described  as  mature, 
because  in  this  way  the  natural  association  of  its  parts  is  most  con- 
cisely indicated.  There  can  be  no  question  that  the  figurative  use  of 
these  organic  terms  has  contributed  greatly  to  the  understanding 
and  the  enlivenment  of  Geography. 

The  preference  and  experience  of  the  teachers  who  use  this  Text 
may  be  called  upon  to  decide  whether  the  Exercises  shall,  step  by 
step,  precede  or  follow  the  study  of  a  text-book.  Good  work  may 
be  done  in  either  order.  References  are  frequently  inserted  in  the 
Text  to  several  recent  text-books,  whereby  the  pupil  is  led  at  once 
to  explanations  or  definitions  needed ;  but,  in  general,  the  Exercises 
are  presented  in  so  great  detail  that  they  are  largely  self-explana- 
tory ;  hence  it  is  relatively  immaterial  whether  they  are  used  before 
or  after  a  text,  as  far  as  the  difficulty  of  the  work  is  concerned ;  but 
it  is  the  belief  of  the  author  that  the  more  scientific  procedure  is 
to  perform  the  Exercises  first  and  to  study  the  corresponding  parts 
of  a  text  afterwards.  In  no  case,  however,  is  it  intended  that  the 
performance  of  the  Exercises  should  replace  the  careful  study  of 
a  text- book,  where  many  subjects  for  which  no  space  can  be  found 
in  a  laboratory  manual  are  introduced  and  concisely  explained  and 
defined. 

>  The  author  desires  to  thank  his  friends,  Professor  D.  W.  Johnson 
of  Harvard  University,  Mr.  Charles  R.  Allen  of  the  New  Bedford 
High  School,  Mr.  Sumner  W.  Gushing  of  the  Salem  Normal  School, 
and  Mr.  W.  L.  W.  Field  of  Milton  Academy,  who  have  patiently 
and  critically  read  the  proof  of  the  Text,  with  the  result  of  con- 
tributing many  practical  suggestions,  greatly  to  the  improvement  of 
the  Exercises.  The  preparation  of  the  Text  and  the  Atlas  has  truly 
been  a  long  and  laborious  task ;  but  it  is  hoped  that  the  labor  thus 
expended  may  not  be  without  its  reward  in  the  way  of  giving  some 


PREFACE  xi 

understanding  and  enjoyment  of  a  great  and  delightful  subject  to 
the  many  students  who  may  not  pursue  it  beyond  an  elementary 
course  in  school  or  college,  but  who  will  frequently  encounter  it  in 
the  world  at  large ;  and  in  the  way  of  providing  a  good  foundation 
for  further  work  by  those  who  wish  to  gain  a  scholarly  acquaintance 
with  Geography  in  more  advanced  courses  of  study. 

W.  M.  D. 
HARVARD  UNIVERSITY 


CONTENTS 


PAGE 

GENERAL  INSTRUCTIONS 1 

EXERCISES 

I.    THE  VALLEY  SYSTEMS  OF  THE  LANDS 3 

II.    A  COASTAL  PLAIN 13 

III.  VALLEYS  IN  A  COASTAL  PLAIN 18 

IV.  PLATEAUS  AND  CANYONS 29 

V.    THE  SCULPTURE  OF  MOUNTAINS 45 

VI.    VOLCANOES  AND  LAVA  FLOWS 66 

VII.    THE  RIVER  CYCLE:    WATERFALLS,  RAPIDS,  AND  GRADED 

RIVERS 80 

VIII.    THE  RIVER  CYCLE  :    RIDGES,  VALLEYS,  AND  RIVER  CAP- 
TURES        88 

IX.    SHORE  LINES 96 

X.    THE  DISTRIBUTION  OF  TEMPERATURE 115 

XI.    THE  PREVAILING  WINDS  OF  THE  WORLD 121 

XII.    WEATHER  MAPS 129 

XIII.    OCEAN  CURRENTS  .  138 


xii 


EXERCISES  IN  PHYSICAL 
GEOGRAPHY 

GENERAL   INSTRUCTIONS 

In  performing  the  exercises  here  presented,  each  pupil  should 
have  this  Manual,  the  accompanying  Atlas,  and  an  ordinary  Note- 
book on  his  desk. 

The  Manual  gives  directions  and  questions.  The  answers  to  the 
questions  are  to  be  found  by  studying  the  figures  in  the  Atlas,  and 
then  they  are  to  be  written  in  the  Notebook.  The  directions  usu- 
ally require  some  simple  drawing  in  the  Atlas  or  Notebook. 

References  to  the  plates  and  figures  of  the  Atlas  are  made  by 
two  numbers ;  the  first  number,  in  smaller  type,  refers  to  the 
plate  ;  the  second  number,  in  larger  type,  refers  to  the  figure.  For 
example,  6  12  means  Plate  6,  Figure  12.  When  a  plate  is  referred 
to  without  mention  of  any  figure,  the  plate  number  is  preceded  by 
the  word  Plate. 

References  to  certain  text-books,  where  explanations  of  various 
topics  may  be  found,  are  made  by  initial  letters,  followed  by  num- 
bers which  indicate  the  page  and  fraction  (ninths)  of  a  page  in- 
tended A  dash  after  a  page  number  indicates  a  longer  reference 
than  usual.  DE  refers  to  Davis's  Elementary  Physical  Geog- 
raphy; DP,  to  Davis's  Physical  Geography;  G,  to  Gilbert  and 
Brigham's  Introduction  to  Physical  Geography ;  T,  to  Tarr's  New 
Physical  Geography.  U.S.G.S.  means  United  States  Geological 
Survey. 

General  explanations  within  a  section  are  often  preceded  by 
the  word  NOTE.  Explanatory  phrases  or  words  are  inclosed  in 

1 


2  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

parentheses  (  ).  Bracketed  [  ]  sections  and  questions  may  be 
omitted  in  a  short  course :  [blue]  and  [red]  suggest  the  use  of 
colored  crayons,  but  they  are  not  essential. 

Scientific  terms,  when  first  used,  are  printed  in  italics ;  they  are 
repeated  in  the  final  section  of  each  exercise  for  review. 

The  letters  N.,  E.,  S.,  W.,  meaning  north,  east,  south,  west,  are 
always  followed  by  a  period.  Italic  capital  letters  without  a  period 
refer  to  the  same  letters  in  the  figures  of  the  Atlas.  Such  refer- 
ences as  DI-DI  mean  Dl}  Z>2,  D3,  -D4.  Further  explanation  of  the 
figures  is  given  at  the  beginning  of  the  Atlas. 

At  the  opening  of  a  day's  exercise  write  in  the  Notebook  the 
number  and  name  of  the  exercise,  and  also  the  number  of  the  sec- 
tion at  which  work  is  begun.  Enter  the  number  of  each  question 
before  its  answer.  When  a  new  section  is  begun,  enter  its  number. 

Head  each  question  or  direction  carefully.  Then  turn  to  the 
proper  figure  in  the  Atlas  and  study  out  the  answer.  Prepare  the 
answer  clearly  in  the  mind  before  writing  it  down ;  then  write  it 
accurately  in  the  Notebook,  and  turn  promptly  to  the  next  question. 

When  the  directions  require  drawing  in  the  Atlas  or  Notebook, 
consider  carefully  what  is  to  be  done  before  doing  it.  See  that 
your  pencil  is  sharp,  or  your  pen  clean,  before  drawing  any  lines. 

Note  that  in  Exercise  V  the  plates  are  used  in  the  following 
order :  11,  12,  14,  13,  16  ;  in  Exercise  VI,  in  order  17,  18,  20,  19,  15 ;  in 
Exercise  VII,  in  order  21,  22,  23,  24,  26 ;  in  Exercise  VIII,  in  order 
27,  25,  28,  29.  This  arrangement  is  made  so  that  the  plates  may  be 
easily  compared  with  each  other.  By  following  the  references  to 
plates  and  figures  as  given  in  the  text  there  will  be  no  difficulty  in 
finding  the  proper  figure. 


EXERCISE  I.   THE  VALLEY  SYSTEMS  OF  THE  LANDS 

OBJECT.    To  explain  the  general  effect  of  rain  and  rivers  on  the  lands. 

Preliminary.  1 1  is  a  bird's-eye  view  of  a  " block"  of  land,  as  if  it 
had  been  cut  out  of  the  earth's  crust.  North  is  toward  the  far  end 
of  the  block.  The  NW.  and  SE.  corners  of  the  block  are  trimmed 
off  to  save  space.  A  mountain  range,  M-^—M^  rises  in  the  middle 
distance  ;  the  land  slopes  from  the  mountain  crest  southward  to  the 
seashore  in  the  foreground,  and  northward  to  an  elevated  interior 
basin  in  the  background,  from  which  no  rivers  escape  to  the  sea. 
A  scale  of  miles  is  marked  on  the  S.  baseline  of  the  block.  The 
scale  of  heights,  on  the  W.  side  of  the  block,  is  exaggerated  about 
ten  times  as  compared  with  the  front  horizontal  scale.  Numbers 
(in  large  type)  to  the  left  of  large  dots  on  the  rivers  indicate 
distances  from  the  sea  in  miles;  numbers  (in  smaller  type) "to  the 
right  of  the  dots  and  on  the  mountains  indicate  altitudes  in  feet. 
This  exercise  uses  1,  2,  1-6. 

1.  1.  How  high  is  the  highest  peak  of  the  mountain  range  in  1 1? 
About  how  far  is  it  from  the  ocean  ?  In  what  direction  does  the 
range  extend  ?  In  what  general  direction  does  river  Y  flow  ? 
2.  Mark  in  light  [blue]  lines  the  path  that  rain  water  would  fol- 
low from  A  to  the  ocean;  from  B-,  from  C;  from  Dt.  3.  Does 
the  greater  part  of  each  path  lie  on  a  hillside  (or  mountain-side) 
slope  or  along  a  valley  bottom  ?  4.  Which  paths  unite  on  the 
way  to  the  ocean  ?  Draw  similar  lines  to  the  ocean  from  D2-D5 ; 
from  E^-Es.  5.  Suppose  a  great  many  such  lines  were  drawn ;  in 
what  part  of  their  paths  would  they  be  separate?  in  what  part 
united  ?  6.  How  are  streams  formed  ?  7.  What  is  meant  by 
ground  water,  and  how  is  it  related  to  rain  and  to  streams  ?  (DE, 
234.3,  236.3  ;  DP,  224.4,  226.8;  G,  100.7,  103.6;  T,  39.1,  59.5.) 

3 


4  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

2.  1.  Where  two  streams  (or  rivers)  unite  (as  near  E±  or  E5),  do 
they  approach  their  junction  at  the  same  level,  as  in  i  2,  or  at  dif- 
ferent levels,  as  in  i  3  ?    2.  In  which  one  of  1  2  and  1  3  may  the  two 
valley  floors  (and  streams)  be  described  as  "  joining  at  accordant 
levels  "  (or  as  making  an  "  accordant  junction  ")  ?  in  which  one 
as  "making  a  discordant  junction"  (or  a  "hanging  junction")  ? 
3.  Do  the  valleys  of  1 1  generally  show  accordant  junctions  or  dis- 
cordant (hanging)  junctions  ?    4.  Mark  [blue]  lines  along  all  the 
streams  which  unite  in  1 1  to  form  river  V.    5.  What  name  is  given 
to  a  system  of  water  courses   consisting  of  a  river  with  all  its 
branches  and  side  streams  ?    (DE,  241.5  ;    DP,  230.3  ;    G,  36.4.) 
6.  What  similar  name  may  be  given  to  all  the  valleys  from  which 
the  streams  unite  to  form  a  single   river  ?     7.  How  many  large 
valley  systems  are  completely  shown  S.  of  the  mountain  crest  in 
1 1  ?    8.  Which  system  is  the  largest  ?     How  long  is  its  longest 
river  ? 

3.  1.  Begin  at  F  in  1 1  and  draw  a  broken  [red]  line  to  inclose 
all  the  land  surface  from  which  the  rainfall  is  discharged  or  drained 
by  the  large  river  V.    2.  Over  how  many  prominent  peaks  (more  than 
4000'  high)  does  the  inclosing  line  pass  ?    3.  Where  does  it  follow 
a  sharp-crested  ridge ?  abroad,  rounded  ridge?  a  narrower  rounded 
ridge  ?    Draw  a  similar  line  for  the  smaller  river  F.    4.  What  name 
is  given  to  the  drainage  areas  thus  inclosed?    to  the  line  sepa- 
rating the  drainage  areas  ?    (DE,  241.9  ;  DP,  230.6  ;  G,  36.3-5.) 
5.  Draw  a  dotted  [red]  line  inclosing  the  valley  or  stream  basin  A  ; 
inclosing  B  ;  Z>3.    6.  Such  lines,  where  they  do  not  follow  the  main 
divides,  may  be  called  subdivides.    Why  ?     7.  Do  spurs  (branches 
of  the  larger  ridges)  usually  form  divides  or  subdivides  ? 

4.  1.  What  is  the  altitude  of  river   F  4  mi.  from  its  mouth  ? 
At  what  distance  from  its  mouth  is  the  altitude  of  river  F  160'  ? 
What  is  the  altitude  of  the  NE.  branch  of  river  V  at  14  mi.  from 
its  mouth  ?     2.  In  2  4  the  baseline  represents  sea  level ;  the  spaces 
between  the  vertical  lines  represent  distances  of  two  miles  ;  how  are 
altitudes  indicated  ?    3.  Mark  on  these  vertical  lines  (beginning  at 


THE  VALLEY  SYSTEMS  OF  THE  LANDS        5 

the  right)  the  altitudes  for  successive  points  on  river  VC.  4.  Draw 
a  curve  through  the  points  thus  marked.  5.  What  does  this  curve 
represent  ?  It  may  be  called  the  profile  of  river  VC.  6.  Does  the 
profile  show  the  true  slope  of  the  river  or  an  exaggerated  slope  ? 
Why?  7.  Mark  a  cross  (x)  on  this  profile  where  stream  B  joins 
river  VC.  From  this  cross  construct  the  profile  of  stream  B.  8.  Do 
the  same  for  river  E2;  for  stream  A.  9.  What  part  of  each  profile 
is  steepest  ?  least  steep  ?  10.  In  what  part  of  the  river  system 
(near  headwaters  or  mouth)  do  the  streams  make  most  of  their  de- 
scent (OT  fair)  toward  sea  level?  11.  What  is  (roughly)  the  descent 
or  fall  of  the  headwater  streams  in  feet  per  mile  ?  of  the  lower 
course  of  river  V?  NOTE:  Large  rivers,  like  the  Mississippi,  flow 
in  their  lower  course  with  a  fall  of  only  an  inch  or  two  in  a  mile. 

12.  In  what  part  of  1 1  will  the  streams  run  fastest  ?  slowest  ?  Why  ? 

13.  Where  are  the  streams  of  smallest  volume  ?  the  rivers  of  great- 
est volume  ?    Explain. 

5.  1.  What  effect  is  (usually)  produced  on  stream  (or  river)  beds 
by  the  action  of  running  water  ?  Explain  (DE,  136.2,  245.7  ;  DP, 
103.7  ;  G,  32.1,  35.2  ;  T,  52.7).  2.  What  change  will  this  action 
gradually  produce  in  the  stream  and  river  profiles  of  1 1  ?  (See  2  4.) 
3.  What  change  has  it  already  produced  ?  4.  How  does  it  happen 
that  the  slope  of  each  river  leads  it  so  accurately  to  sea  level  at  the 
river  mouth  ?  5.  In  this  connection,  how  can  use  be  made  of  the 
phrase  river  erosion?  of  the  term  baselevel?  NOTE  :  The  ocean  sur- 
face may  be  called  the  general  baselevel  of  erosion  for  the  continents, 
because  it  is  the  "  level  base,"  closer  and  closer  to  which  the  proc- 
esses of  erosion  tend  to  wear  down  or  degrade  the  land.  6.  In  what 
part  of  the  V  river  system  can  the  valleys  still  be  most  worn  down 
or  degraded  ?  Why  ?  7.  Will  long-continued  river  action  tend  to 
change  1  2  to  i  3,  or  1 3  to  1  2  ?  8.  By  what  process  do  you  think  the 
accurate  accordance  of  the  branching  valleys  with  each  other,  and 
of  the  main  valley  with  sea  level,  in  1 1  has  been  brought  about  ? 
9.  Has  the  production  of  the  valley  system,  with  its  accordant  ar- 
rangement of  parts,  probably  required  a  very  long  or  a  short  time  ? 


6  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

6.  1.  What  is  the  effect  of  weather  changes,  acting  for  a  long 
time,  on  a  land  surface  ?    Explain  briefly.    (DE,  134.8  ;  DP,  99.8  ; 
G,  78.8;   T,  38.6.)     2.  How  may  the  terms  weathering,  rock  ivaste 
(or  land  waste),  and  soil  be  used  in  connection  with  valley  A  (or 
other  parts)  of  i  1  ?    3.  Rain  water  runs  down  hillside  slopes  in  wet 
weather,  forming  little  rills.    4.  How  will  the  wet-weather  rills  act 
on  the  hillside  waste  (or  soil)  ?    5.  What  change  will  thus  be  made 
in  the  size  of  the  hills  ?     6.  Will  this  change  take  place  rapidly  or 
slowly  ?    7.  What  is  the  chief  source  of  the  water  in  the  streams 
during  dry  weather  ?    8.  Why  do  most  streams  and  rivers  become 
(comparatively)  clear  when  running  slowly  at  times  of  low  water 
in  dry  weather,   and  muddy  or  turbid  when  running  rapidly  at 
times  of  flood  in  wet  weather  ?    NOTE  :  The  destructive  processes 
caused  by  weather  changes  and  stream  (river)  action  may  together 
be  given  the  general  name  erosion.     9.  State  some  of  the  effects 
already  produced  by  erosion  in  1 1  near  A  ;    near  Dl  •    near  Ez. 
10.  State  some  effects  yet  to  be  produced  near  the  same  points. 

7.  1.  Is  a  greater  or  less  stream  velocity  needed, to  wash  along, 
or  transport,  coarse  waste  (bowlders  and  gravel)  than  fine  waste 
(sand,  in  small  grains  ;  silt,  in  very  small  particles)  ?    2.  In  what 
part  of  its  system  can  a  river  transport  both  coarse  and  fine  waste  ? 
only  the  finer  waste  ?    3.  Is  a  river  a  better  transporter  at  time  of 
flood  or  of  low  water  ?    4.  What  happens  to  coarse,  angular  waste 
as  it  is  rolled  along  the  bed  of  a  rapid  stream  ?    5.  To  what  part 
of  1 1  will  the  waste  from  the   V  valley  system  be  transported  ? 
of  the  F  valley  system  ?   6.  Why  is  some  of  the  waste  laid  down, 
or  deposited,  near  the  river  mouths  ?    7.  What  is  the  form  of  the 
land  that  has  been  made  of  rock  waste  deposited  by  rivers  near 
their  mouths  ?    8.  What  name  is  given  to  such  forms  ?  Mark  them 
with  [blue]  dots  in  1 1.    9.  Do  these  forms  contain  all  the  waste 
that  has  been  brought  to  the  river  mouths  from  the  headwaters 
and  slopes   of  the   valley   systems  ?     10.  Where   is   the  rest  of 
the  waste  deposited  ?    [11.  How  is  some  of  this  deposit  indicated 
in  the  S.  block  face  of  1 1  ?     12.   How  has  it  been  spread  out  ? 


THE  VALLEY  SYSTEMS  OF  THE  LANDS  7 

13.  Why  is  it  deposited  in  layers  or  strata?  14.  Has  each  layer 
or  stratum  a  smooth  or  a  rough  surface  ?  15.  Why  does  the  sea- 
bottom  deposit  vary  in  thickness,  as  shown  on  the  S.  face  of  the 
block  ?]  16.  State  the  general  principle  thus  illustrated  concern- 
ing the  removal  of  land  waste.  (DE,  136.1 ;  DP,  103.6  ;  G,  59.8  ; 
T,  52.5.) 

8.  [1.  Suppose  that  the  processes  of  erosion,  transportation,  and 
deposition  continue  many  hundred  thousand  years.    2.  Draw  in  2  4 
a  broken  line  to  show  the  profile  which  would  then  be  followed 
by  river  VC  (begin  the  river  head  at  2600')  ;  a  dotted  line  to  show 
the  profile  at  a  still  later  time  (begin  the  river  head   at  1800'). 
XOTE  :    The  river  profile  must  have  a  seaward  slope,  less  steep 
toward  the  mouth  than  toward  the  head;    it  must  not  be  drawn 
beneath  sea  level.    3.  Which  part  of  the  river  shows  the  greatest 
change  in  these  profiles  ?  the  least  change  ?    Why  ?    4.  Will  the 
river  then  run  faster  or  slower  than  now  ?  transport  more  or  less 
waste  than  now?  Why  ?    5.  Imagine  that  the  processes  of  erosion, 
transportation,  and  deposition  have  already  been  at  work  many 
hundred  thousand  years  before  the  hills  and  valleys  gained  the 
form  shown  in  1 1.    6.  Draw  in  2  4  a  profile  for  an  early  stage  of 
river  VC  ;    for  a  still  earlier  stage.     (The  dot-and-dash  line  in  2  4 
may  be  taken  to  represent  the  original  profile  of  the  land,  before 
the  valleys  were  eroded.    Some  early  river  profiles  are  partly  indi- 
cated by  three-dot  lines.)  7.  Compare  the  profile  for  1 1  with  the 
earlier  profiles,   as  to  the  slope   of  the   main  river  (near  middle 
course)  ;  as  to  the  slope  of  headwaters.    Explain  the  differences. 
8.    On  which  profile  would  the  main  river  (middle  course)  flow 
fastest  ?   slowest  ?    erode  its  bed  fastest  ?  slowest  ?    [9.  Explain 
as  fully  as  you  can.]    10.  Answer  the  same  (four)  questions  for 
the   headwaters.     [11.  Explain.]     12.  As    the    river   profiles  are 
worn  lower  and  lower,  what  happens  to  the  hillsides  and  hilltops  ?] 

9.  If  §  8  is  omitted,  §§  9, 10  should  also  be  omitted.    [1.  In  2  6  MM 
is  a  profile  (on  a  larger  scale  than  1 1)  across  one  valley  and  two 
ridges  about  ten  miles  from  the  sea.    A  similar  cross  profile  of  the 


8  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

same  valley  for  an  earlier  stage  of  its  history  is  indicated  by  YY; 
for  a  later  stage  by  00.  Draw  a  profile  for  a  stage  between  Y  and 
M ;  another,  between  M  and  0.  2.  In  which  stage  has  the  valley 
the  narrowest  floor  and  the  steepest  sides  ?  Why  ?  3.  In  which 
stage  the  widest  floor  with  the  most  gently  sloping  sides  ?  Why  ? 
4.  Draw  several  additional  profiles  (one  earlier  than  YY,  one  later 
than  OO).  5.  Describe  the  form  that  the  district  would  have  when 
all  its  valleys  come  to  have  cross  profiles  like  the  latest  profile. 
6.  Why  may  such  a  district  be  called  a  peneplain  ?  What  is  the 
relation  of  a  peneplain  to  its  baselevel  ?  (DE,  206.2  ;  DP,  152.5  ; 
G,  161.4  ;  T,  58.5.)  7.  In  which  stage  are  the  valleys  deepened 
faster  than  the  hills  are  worn  down  ?  In  which  stage  are  the  hills 
worn  down  faster  than  the  valleys  are  deepened  ?  [8.  Explain  as 
fully  as  you  can.]  9.  In  which  stage  are  the  hills  worn  down 
most  slowly  ?  Why  ?  10.  Why  are  the  hills  worn  down  faster  in 
this  stage  than  the  valleys  are  then  deepened  ?] 

10.  If  §  9  is  omitted,  omit  §  10  also.  [1.  In  which  profile  of 
2  4  might  the  river  be  appropriately  called  young  ?  old  ?  2.  In 
which  cross  profiles  of  2  6  might  the  valley  be  called  young  ?  old  ? 
3.  What  term  (indicating  stage  of  development)  might  be  as  appro- 
priately applied  to  the  cross  profile  of  the  valley  MM,  2  6  ?  to  the 
river  VC,il?  (DE,  269.8 ;  DP,  250.6  ;  G,  58.3  ;  T,  57.3.)  4.  If  an 
old  land  surface  or  peneplain  were  very  slowly  given  a  greater 
altitude  by  a  broad  uplift  of  its  region,  what  change  would  take 
place  in  the  behavior  of  its  rivers  ?  5.  Why  might  the  rivers  then 
be  described  as  "  made  young  again  "  ?  or  as  rejuvenated  ?  or  as 
revived  ?  6.  What  event  presumably  took  place  in  the  region  of  1 1, 
before  young  valleys  could  be  eroded  ?  Why  ?  NOTE  :  The  long 
period  of  time  in  which  the  general  processes  of  erosion  will  wear 
down  any  uplifted  region  to  a  low  peneplain  may  be  called  a  cycle 
of  erosion.  The  features  of  the  land  surface  in  the  early,  inter- 
mediate, and  late  stages  of  a  cycle  may  be  spoken  of  as  young, 
mature,  and  old.  7.  Compare  young  and  old  rivers,  as  to  slope  ;  as 
to  velocity ;  as  to  the  power  of  transportation  ;  as  to  rate  of  valley 


THE  VALLEY  SYSTEMS  OF  THE  LANDS  9 

deepening.  8.  Compare  the  rivers  of  1 1  with  young  rivers  and 
with  old  rivers,  as  to  form  of  profile  (see  24);  as  to  depth  of 
valleys  (see  2  6)  ;  as  to  rate  of  valley  deepening  ;  as  to  amount 
of  waste,  or  load,  received  from  the  valley  sides  ;  as  to  texture 
(coarseness  or  fineness)  of  waste  received.  9.  Compare  the  valleys 
of  a  river  system  in  its  young,  mature,  and  old  stages,  as  to  depth 
(below  the  neighboring  hills) ;  as  to  narrowness  or  openness  ;  as 
to  slope  of  valley  sides.  NOTE  :  The  relief  of  a  land  surface 
is  the  general  difference  of  altitude  between  the  valleys  and  the 
neighboring  hilltops,  or  the  height  of  the  hills  above  the  neighbor- 
ing valleys.  10.  In  what  stages  of  a  cycle  of  erosion  is  the  relief 
of  moderate  measure  (see  26)  ?  of  greatest  measure  ?  11.  In  what 
stage  of  a  cycle  of  erosion  might  the  rivers  be  imagined  as  saying 
to  one  another,  "Our  work  is  before  us"?  "Our  work  is  well 
advanced"?  "Our  work  is  (nearly)  done"?  12.  Describe  briefly 
the  "  life  history  of  a  river  system."] 

11.  1.  Describe  the  form  of  the  land  margin  at  N  and  Nlf  1 1. 
Compare  it  with  the  margin  near  the  river  mouths.    2.  How  have 
the  cliffs  at  N  and  ^  been  produced  ?  (DE,  136.8  ;  DP,  104.3 ;  G, 
309.9  ;  T,  211.3.)    3.  Why  do  the  sea  cliffs  not  extend  all  along  the 
shore  ?    4.  Why  are  they  higher  in  some  places  than  in  others  ? 
5.  Why  are  some  of  the  cliffs  not  now  at  the  shore  line  ?  6.  What 
becomes  of  the  land  waste  that  is  weathered  from  the  cliff  face 
or  worn  from  the  cliff  base  ?    NOTE  :    The  destructive  processes 
going  on  along  the  cliff  base  and  on  the  shallow  sea  bottom  near 
shore  may  be  called   marine  erosion,  in   contrast  to  the   general 
erosion  of  the  land  surface,  which  may  be  called  subaerial  erosion 
(the  work  of  weathering,  and  of  rills,  streams,  and  rivers  being 
here   included).    7.  Which   process,    marine   erosion   or   subaerial 
erosion,  works   on   the  greatest  amount  of  land    surface   in  1 1  ? 
8.  Which  process  probably  gives  the  greatest  amount  of  waste  to 
the  sea  ? 

12.  1.  Draw  a   [red]   line  in  1 1   dividing   the  surface  that  is 
drained  to  the  ocean  from  that  drained  to  the  interior  lake.    2.  The 


10  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

lake  occupies  the  lowest  part  of  an  inclosed  or  interior  basin.  Has 
the  lake  an  outlet  ?  3.  What  is  the  (local)  baselevel  for  the  streams 
that  flow  into  the  lake  ?  4.  Where  do  these  streams  deposit  the  waste 
that  they  bring  from  their  upper  valleys  ?  5.  As  time  passes,  will 
the  waste-covered  plain  bordering  the  lake  be  worn  lower  (degraded) 
or  built  higher  (aggraded)?  6.  How  will  this  change  affect  the  base- 
level  of  the  interior  basin  ?  7.  How  does  the  water,  supplied  by  the 
inflowing  streams,  escape  from  the  lake?  (DE,  284.1;  DP,  305.1  ; 
T,  163.7.)  8.  If  you  were  in  camp  on  the  lake  shore  near  a  stream 
mouth,  where  would  you  get  your  drinking  water  ?  Explain. 

13.  1.  2  5  is  a  map  (roughly)  representing  the  SW.  part  of  1 1, 
from  the  mountain  crest  to  the  shore  line.  Print  the  letters  V  and 
Y  on  2  5  in  places  corresponding  to  V  and  F  in  1 1  ;  also  the  let- 
ters C,  Ms,  M1}  D1}  D3,  Dr0,  N.  2.  In  25  how  are  the  streams  rep- 
resented ?  the  main  divides  and  the  subdivides  ?  the  borders  of  the 
flat  valley  floors  ?  3.  Draw  a  broken  [red]  line  inclosing  the  drain- 
age basin  of  river  F.  4.  What  is  (about)  the  length  of  river  F?  the 
breadth  of  the  ridge  between  the  upper  parts  of  valleys  Y  and  V? 

5.  In  what  direction  would  wet-weather  rills  flow  at  A  ?    at  B  ? 

6.  What  relation  exists  between  the  direction  of  rill  flow  and  the 
direction  of  the  numerous  lines  near  A  and  B  ?    NOTE  :  These  lines 
may  be  called  "  down-slope  lines,"  or  hachures  (pron.  hashures). 
They  are  drawn  in  belts  around  the  slopes  ;  they  should  be  long  and 
light  on  gentle  slopes,  shorter  and  darker  on  steep  slopes.  [Hachures 
should  seldom  be  drawn  perfectly  straight  or  precisely  parallel  to 
each  other  ;  they  should  usually  be  a  little  curved,  and  more  or  less 
divergent  or  convergent  downhill.    In  the  upper  part  of  2  5  the 
hachures  are  drawn  somewhat  darker  and  closer  together  on  the  E. 
and  SE.  slopes,  so  as  to  give  more  effect  of  relief.]    7.  What  is  the 
arrangement  of  the  hachures  at  the  head  of  a  valley  ?  around  the 
end  of  a  spur  ?    8.  What  process,  described  in  §  6,  takes  place  along 
the  down-slope  lines  represented  by  the  hachures  ?    [9.  Shade  with 
carefully  drawn  hachures  the  upper  part  of  the  valley  in  which  D3 
or  D5  lies  ;  one  of  the  spurs  between  D3  and  Z>5.    (The  three-dot  lines 


THE   VALLEY   SYSTEMS   OF   THE   LANDS  11 

may  be  used  to   guide  the  hachure  belts.)     10.  Draw  additional 
hachures  in  the  NW.,  SW.,  or  NE.  parts  of  2  5.] 

14.  1.  How  many  miles  are  shown  on  the  scale  at  the  bottom  of 
25?    2.  How  can  you  measure  distances  on  the  map,  2  5,  by  this 
scale  ?    3.  Why  may  such  a  scale  be  called  a  linear  scale  ?    4.  Be- 
ginning at  0  on  the  linear  scale,  mark  points  an  inch  apart  along 
the  scale  ;  how  many  miles  are  represented  by  an  inch  on  the  scale  ? 
5.  Complete  the  sentences :  "  The  scale  of  2  5  is  -    —  miles  to  an 

inch";     "In  the   front  scale  of  1 1,  (fraction)   of  an   inch 

represents  a  mile."    6.  How  many  inches  make  a  mile  ?    7.  What 
fraction  of  an  actual  distance  would  represent  it  on  a  map  of  which 
the  scale  is  a  mile  to  an  inch  ?  on  a  map  with  a  scale  of  two  miles 
to  an  inch  ?  [half  a  mile  to  an  inch  (or  two  inches  to  a  mile)  ?  ten 
miles  to  an  inch?]  on  25?    8.  About  what  scale  is  represented  by 
the  fraction     *    ?  —  - ?   r    '     9       '      ?      '     ?      l     ?"|     q   Wh v  mav 

U     i;LV»i«l  '      125,000  '      L250,IKH)  "      1,<ICU,UUU  '      30,<IOO  '      10,000   '  J        "'     Y  *      J       UdV 

any  one  of  these  fractions  be  called  a  fractional  scale  ? 

15.  [1.  Over  a  century  ago  John  Playfair,  of  Edinburgh,  Scot- 
land, wrote  as  follows  :    "  Every  river  appears  to  consist  of  a  main 
trunk,  fed  from  a  variety  of  branches,  each  running  in  a  valley  pro- 
portionate to  its  size,  and  all  of  them  together  forming  a  system  of 
valleys,  communicating  with  one  another  and  having  such  a  nice 
[accurate]  adjustment  of  their  declivities  that  none  of  them  join  the 
principal  valley  either  on  too  high  or  too  low  a  level  ;  a  circum- 
stance which  would  be  infinitely  improbable.if  each  of  these  valleys 
were  not  the  work  of  the  stream  that  flows  in  it.  ...    When  the 
usual  form  of  a  river  is  considered,  the  trunk  divided  into  many 
branches  which  rise  at  a  great  distance  from  one  another,  ...  it 
becomes  strongly  impressed  upon  the  mind  that  all  these  channels 
[valleys]  have  been  cut  by  the  waters  themselves ;  that  they  have 
been  slowly  dug  out  by  the  washing  and  erosion  of  the  land  ;  and 
that  it  is  by  the  repeated  touches  of  the  same  instrument  that  this 
curious  assemblage  of  lines  [valleys]  has  been  engraved  so  deeply 
on  the  surface  of  the  globe."    (Quoted   from  Illustrations  of  the 
Huttonian  Theory  of  the  Earth,  Edinburgh,   1802,  pp.  102,  103.) 


12 


EXERCISES  IN  PHYSICAL   GEOGRAPHY 


2.  What  facts,  mentioned  in  the  above  quotation,  are  illustrated  in 
this  exercise  ?  3.  What  suppositions  or  theories  presented  in  the 
quotation  are  supported  by  this  exercise?]  [4.  The  illustration  be- 
low represents  a  model  which  shows  mountains  bordering  the  sea. 
Name  some  features  there  represented  which  have  been  studied  in 
this  exercise.] 

16.  Define  the  following  terms  :  §  1,  ground  water ;  §  2,  river 
system,  valley  system,  accordant  and  discordant  (or  hanging)  valley 
junctions  ;  §  3,  drainage  area,  ridge,  peak,  spur,  river  basin,  divide 
or  water  parting,  subdivide ;  §  4,  river  profile ;  §  5,  river  erosion, 
baselevel  of  erosion,  degrade;  §  6,  weathering,  rock  waste,  land  waste, 
soil,  rill ;  §  7,  bowlders,  gravel,  sand,  silt,  transport,  deposit,  delta, 
[stratum,  strata]  ;  [§  9,  peneplain  ;  §  10,  revived  river,  cycle  of  ero- 
sion, texture  of  river  load,  relief  ;]  §  11,  sea  cliff,  marine  erosion, 
subaerial  erosion ;  §  12,  interior  basin,  aggrade  ;  §  13,  hachures ; 
§  14,  linear  scale,  fractional  scale. 


EXERCISE  II.   A  COASTAL  PLAIN 

OBJECT.  To  represent  part  of  a  coastal  plain  on  a  map,  and  to  describe 
the  form  thus  represented. 

Preliminary.  The  numbers  on  si  show  the  altitude  or  height 
above  sea  level,  in  feet,  of  many  points  (dots  near  the  numbers)  in 
a  district  bordering  the  sea.  The  numbers  preceded  by  a  negative 
sign  (as  — 15)  indicate  a  negative  altitude  ;  that  is,  a  depth  below 
sea  level.  This  exercise  uses  3  1,  3  2  (and  4  8)  ;  [also  6  15  and  35  1]. 

1.  1.  Draw  a  light  (pencil)  line  in  3 1  separating  all  parts  of 
the  surface  that  are  higher  than  100'  from  all  parts  that  are  lower 
than  100'.    This  line  must  pass  through  all  points  marked  100  ;  mid- 
way between  points  equally  above  and  below  100,  such  as  105  and 
95 ;  nearer  to  95  than  to  110  ;  nearer  to  105  than  to  90.    2.  Ex- 
plain the  preceding  rules.     3.  Draw  similar  lines  separating  parts 
higher  and  lower  than  200';  than  300';    than  0'.     Mark  the  last 
line  heavier  than  the  others.   What  does  this  line  represent  ?   4.  Do 
the   same  for  400',  500',  600'.     [Intermediate  lines  for  50',  150', 
250',  etc.,  may  also  be  drawn.] 

2.  1.  Would  you  ascend  or  descend  (go  uphill  or  downhill,  up- 
slope  or  down-slope)  in  walking  from  K  to  A  ?  from  G  to  H  ?  from 
H  to  F?  from  C  to  E  ?  along  the  100'  line  ?  along  any  of  the  lines 
that  you  have  drawn  ?    2.  Do  the  (pencil)  lines  follow  slanting  or 
level  paths  ?  Lines  of  this  kind  are  called  contour  lines,  or  contours. 
3.  What  is  the  (estimated)  difference  of  altitude  between  H  and  G  ? 
between  B  and  A  ?  between  two  adjoining  contour  lines  ?    4.  The 
last  difference  is  called  the  contour  interval.    WThy  ? 

3.  1.  Lay  a  strip  of  paper  on  3  1  along  the  line  AB  ;  mark  short 
lines  on  the  edge  of  the  strip  opposite  A  and  B  and  print  these  let- 
ters +1'ere;  mark  dots  on  the  strip  edge  at  the  contours  of  0',  100', 

13 


14  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

200',  [250'],  300',  and  600',  and  indicate  by  figures  the  altitude  at 
each  contour  dot.  2.  Now  place  the  strip  along  the  baseline  of  3  2  ; 
lay  off  the  contour  dots  between  A'  and  B',  and  indicate  the  alti- 
tudes to  which  the  dots  refer.  3.  Copy  the  vertical  scale  at  A'  on 
the  edge  of  a  slip  of  paper ;  lay  the  slip  square  across  the  baseline 
A'B'  at  the  successive  contour  dots,  and  mark  off  points  at  the  alti- 
tudes of  the  corresponding  contours  above  A'B'.  4.  Draw  a  line 
through  the  points  thus  determined,  and  prolong  it  to  the  right  of 
B'.  5.  What  does  this  line  represent  ?  It  is  called  a  profile  line,  or 
profile. 

4.  1.  If  you  followed  the  path  of  the  profile  AB  (or  any  similar 
path)  across  3  1,  on  what  part  of  it  would  you  find  a  steep  slope  ? 
a  gentle  slope  ?    2.  How  is  the  difference  of  slope  indicated  by  the 
contour  lines  ?     Explain.    3.  Make  a  general  rule  to  show  how  the 
spacing  of  contour  lines  indicates  steep  and  gentle  slopes.    4.  Draw 
some  short  lines  (about  £"  long)  to  show  the  direction  of   slope 
(downhill)  near  G ;  some  fainter  and  longer  lines  (about  £"  long) 
to  show  the  slope  near  H\  near  C.    5.  The  down-slope  lines  may 
be  called  hachures  (pron.  hashures).    6.  What  is  the  relative  direc- 
tion of  contours  and  hachures  ?    7.  Draw  a  dotted  line  in  3  1  sep- 
arating the  part  of  gentle  slope  from  the  part  of  steeper  slope. 
NOTE  :   In  the  district  here  represented  all  the  land  higher  than 
the  dotted  line  is  supposed  to  be  made  of  resistant  rocks  covered 
with  a  stony  soil  ;  all  the  land  of  less  altitude,  of  layers  or  strata 
of  sand,  gravel,  clay,  etc. ;  each  layer  or  stratum  slants  gently  sea- 
ward with  the  slope  of  the  surface,  and  contains  shells  of  marine 
animals  similar  to  those  living  in  the  neighboring  ocean. 

5,  1.  Describe  the  general  form  of  the  district  in  3  1.    2.  What 
is  the  origin  of  the  gently  sloping  plain?    (DE,  145.2;  DP,  119.9; 
G,  151.8 ;   T,  72.7.)    What  statements  in  §  4  indicate  this  origin  ? 
3.   Which  part  of  the  plain  first  rose  above  the  sea?    4.  What  is 
the  present  altitude  of  the  former  shore  line  ?    the  breadth  of  the 
plain  ?  the  slope  (or  fall)  of  the  plain  in  a  mile  ?  the  direction  of 
the  slope  (north  is  at  the  top  of  the  map)  ?  5.  Print  carefully  on 


A  COASTAL  PLAIN  15 

the  proper  parts  of  si  the  words  :  COASTAL  PLAIN,  OLDLAND, 
OCEAN,  [FORMER  SHORE  LINE,  NEW  SHORE  LINE].  6.  Draw  in  32  a  hori- 
zontal line  showing  the  sea  level  as  it  formerly  appeared.  7.  What 
was  then  the  altitude  of  A  ?  of  G  ?  the  depth  of  F?  of  L  ?  8.  How 
great  an  uplift  of  the  land  with  respect  to  the  sea  has  taken  place  in 
laying  bare  the  coastal  plain  of  3  1  ?  9.  What  would  have  been  the 
breadth  of  the  plain  if  the  uplift  had  been  150'  (see  3  2)  ?  300'  ? 
10.  Make  a  general  statement  showing  the  relation  between  the 
amount  of  uplift  along  the  border  of  a  continent  and  the  breadth 
of  the  resulting  coastal  plain.  [11.  Expand  this  statement  so  as 
to  include  also  the  effect  of  greater  or  less  slope  of  the  sea  bottom 
before  uplift.]  12.  What  can  you  say  as  to  the  cause  of  such 
regional  "  uplifts "  as  are  here  considered  ?  (DE,  158.4 ;  DP, 
132.2.)  NOTE  :  It  is  important  to  remember  that  such  movements 
of  the  earth's  crust  as  are  here  considered  take  place  very  slowly, 
and  require  thousands  and  thousands  of  years. 

6.  1.  Imagine  that  the  region  of  3  1  had  not  been  uplifted,  and 
that  you  stood  at  G.    The  view  before  you  might  then  have  been 
described  as  follows  :  "  I  see  a  rather  steep  hillside  sloping  south- 
ward to  the  seashore,  which  extends  about  east  and  west."    2.  If 
you  were  at  G  after  the  uplift  of  the  region,  how  would  you  describe 
the  view  ?    [3.  Examine  4  7  of  the  next  exercise.    What  is  its  con- 
tour interval  ?    4.  In  what  direction  does  its  coastal  plain  slope  ? 
5.  How  wide  is  it  at  the  E.  end  of  the  map  ?  at  the  W.  end  ?  6.  What 
is  the  greatest  altitude  of  the  oldland  there  shown  ?  7.  What  is  the 
altitude  of  the  former  shore  line  at  the  E.  end  of  the  map  ?  at  the 
W.  end  ?    8.  In  which  part  of  this  plain  was  the  uplift  greatest  ? 
9.  Why  does  the  breadth  of  the  plain  vary  ?    10.  What  would  be 
its  probable  breadth  30  mi.  farther  E.  ?  30  mi.  farther  W.  ?    11.  In 
which  direction,  and  how  far,  would  you  have  to  go  to  find  the 
breadth  of  the  plain  reduced  to  nothing  ?    Explain.] 

7.  1.   Describe  the  forms   shown  in  4  8,  using  the  terms  that 
you  have  printed  on  3  1.     NOTE  :   4  8  is  from  a  photograph  of  a 
narrow  coastal  plain  (looking  NE.)  in  a  bay  on  the  W.  coast  of 


16  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

Scotland ;  it  shows  the  natural  appearance  of  a  small  example  of 
such  forms  as  are  drawn  in  the  outline  maps  and  diagrams  of  this 
exercise.  2.  The  inner  border  of  this  coastal  plain  is  25'  above 
sea  level.  How  much  elevation  of  the  land  (or  depression  of  the 
sea)  must  have  taken  place  when  the  plain  was  laid  bare  ?  [3.  Draw 
a  map,  in  hachures  or  contours,  of  the  district  shown  in  4  8. 
(Assume  such  heights  and  distances  as  seem  appropriate,  and 
choose  your  own  scale  for  the  map.)]  [4.  Examine  6  15.  What 
part  of  what  state  is  there  shown  ?  What  ocean  bounds  it  on  the  W.  ? 
5.  Locate  it  on  Plate  40.  NOTE  :  The  map,  6  15,  is  copied  from 
parts  of  two  contour  maps  published  by  the  United  States  Geolog- 
ical Survey  in  Washington,  D.C.  It  exhibits  the  natural  irregular- 
ities of  the  oldland  hills  and  the  coastal-plain  rivers  which  are 
shown  in  simplified  form  in  these  exercises.  6.  From  what  original 
maps  is  6  15  taken  ?  7.  What  is  its  scale  ?  its  contour  interval  ? 
8.  What  length  of  the  coastal  plain  is  there  shown  ?  what  breadth  ? 
what  is  the  altitude  of  its  inner  border  ?  the  average  slope  (feet 
per  mile)  to  the  sea?  the  direction  of  the  slope?  9.  How  many 
streams  run  from  the  oldland  toward  the  ocean  ?  NOTE  :  Several 
streams  cannot  reach  the  ocean  directly,  because  of  a  long  sand 
reef  that  has  been  formed  along  part  of  the  shore  by  the  sea  waves 
and  currents.  10.  Mark  a  point  (x)  on  the  oldland  from  which 
you  could  get  a  good  view  of  the  plain.  What  is  the  altitude  of  the 
point  ?  its  distance  from  the  inner  border  of  the  plain  ?  from  the 
ocean?  11.  Describe  the  view  from  this  point,  looking  W.,  NW., 
and  SW.] 

8.  [1.  The  lowering  of  lake  waters  may  produce  a  lacustrine 
coastal  plain,  similar  in  many  respects  to  the  marine  coastal  plains 
thus  far  described.  Explain.  2.  The  land  next  S.  of  lake  Erie  pre- 
sents an  example  of  a  lacustrine  coastal  plain,  part  of  which  is 
shown  in  35.1.  3.  In  what  state  does  this  example  occur?  Locate 
it  on  Plate  40.  4.  The  base  of  the  gently  sloping  oldland  is  at 
an  altitude  of  (about)  790';  shade  the  oldland  lightly  (in  pencil). 
5.  How  broad  is  the  plain  ?  What  is  its  average  fall  in  feet  per 


A  COASTAL  PLAIN 


17 


mile  ?  (Do  not  include  the  fall  of  the  shore-line  cliff.)]  [6.  Draw 
on  a  scale  of  10  mi.  to  an  inch,  with  50'  contour  interval,  a  contour 
map  of  part  of  a  coastal  plain,  about  25  mi.  wide,  sloping  a  little  N. 
of  E.,  with  the  former  shore  line  at  (about)  250'  altitude  and  the 
oldland  reaching  650',  5  or  6  mi.  W.  of  the  former  shore  line. 
7.  What  is  the  average  fall  of  the  coastal  plain?  of  the  oldland?] 
[8.  The  illustration  below  represents  a  model  which  shows  a  dis- 
trict bordering  on  the  sea.  What  features,  there  represented,  have 
been  studied  in  this  exercise?] 

9.  Define  the  following  terms  :  §  2,  contour  line,  contour  inter- 
val j  §  3,  profile ;  §  4,  stratum,  strata ;  §  5,  coastal  plain,  oldland ; 
[§  8,  lacustrine  coastal  plain]. 


EXERCISE  III.  VALLEYS  IN  A  COASTAL  PLAIN 

OBJECT.  To  learn  the  forms  produced  in  coastal  plains  by  rivers  and 
streams. 

Preliminary.  If  a  coastal  plain,  like  the  one  shown  in  3  1  of  the 
preceding  exercise,  were  followed  for  a  few  miles  parallel  to  the 
shore  line,  a  river  might  be  found  flowing  from  a  deep  valley 
in  the  oldland  and  crossing  the  plain  in  a  shallow  valley  to  the 
sea.  4  1  is  a  block  diagram  (bird's-eye  view)  of  such  a  river  cross- 
ing a  narrow  coastal  plain.  (The  NW.  and  SE.  corners  of  the  block 
are  cut  off  to  save  space.)  Level  lines,  like  contours,  are  drawn  on 
the  plain,  slanting  lines  on  the  oldland  and  on  the  valley  side. 
The  numbered  lines  show  the  altitude  of  different  parts  of  the 
plain,  valley,  and  oldland.  The  heights  are  much  exaggerated  com- 
pared to  the  horizontal  distances.  The  smooth  valley  floor  may  be 
covered  with  water  when  the  river  is  in  flood,  and  hence  may  be 
called  the  river  flood  plain.  NOTE  :  The  more  natural  appearance 
of  part  of  such  a  plain  and  valley  is  shown  in  4  1  a :  here  the  up- 
land is  divided  into  cultivated  fields,  and  the  valley  side  is  covered 
with  trees.  This  exercise  uses  4,  5,  c,  1-15  (and  3  6) ;  [also  35 1-4]. 

1.  1.  Which  is  higher,  the  coastal  plain  or  the  flood  plain  in 
4  1  ?  How  much  higher  at  G  ?  at  //  ?  at  F  ?  2.  What  is  the  height 
interval  between  the  numbered  contour  lines  ?  3.  Look  at  the  10' 
contour  line  at  G.  Does  it  turn  N.  or  S.  in  passing  from  the  E. 
part  of  the  coastal  plain  to  the  E.  side  of  the  valley  ?  4.  Why  does 
it  turn  in  this  way  ?  5.  How  does  it  turn  at  //  from  the  valley  side 
to  the  valley  floor  ?  6.  How  do  you  suppose  it  turns  from  the  val- 
ley floor  to  the  W.  valley  side  ?  from  the  W.  valley  side  to  the 
W.  part  of  the  plain  at  K?  1.  Complete  the  20'  contour  on  the 
E.  valley  side. 

18 


VALLEYS  IN  A  COASTAL  PLAIN          19 

2.  1.  4  2  is  a  map  of  the  same  coastal  plain.    The  top  and  bottom 
of  the  valley  sides  are  marked  with  dotted  lines.    2.  Complete  the 
10'  and  20'  contours  on  the  W.  side  of  the  valley ;  draw  some  hachures 
on  the  valley  side  ;  draw  the  15'  and  25'  contours.    3.  Notice  that  the 
contours  bend  as  they  pass  from  the  plain  to  the  valley  sides.    Com- 
pare the  direction  of  this  contour  bend  with  the  direction  of  slope 
of  the  plain ;  with  the  direction  of  river  flow.    4.  Notice  that  the 
contours  make  a  loop  in  crossing  the  valley.    Is  the  loop  open  up- 
stream or  downstream  ?    5.  Does  the  space  within  the  loop  become 
wider  upstream  or  downstream  ?    [6.  Why  ?]    7.  What  is  the  altitude 
of  the  plain  at  C  ?  at  D  ?  of  the  valley  floor  at  E  ?  at  F  ?    8.  What 
point  on  the  river  is  at  the  same  altitude  as  point  K  (or  G)  on  the 
plain  ?  as  point  B  ?     9.  What  points  on  the  plain  are  of  (about) 
the  same  altitude  as  F  on  the  river  ?  as  E  ?    10.  How  deep  below 
the  coastal  plain  is  the  valley  floor  at  E  ?    at  F?    11.  If  a  village 
were  at  F,  its  people  might  speak  of  the  neighboring  coastal  plain 
as  "the  upland."    Why  ?     [12.  Describe  the  view  from  A,  looking 
W. ;  looking  SW. ;  from  B,  looking  E. ;  looking  N.] 

3.  1.  Compare  the  direction  in  which  the  plain  slopes  with  the 
general  direction  in  which  the  river  flows.    2.  What  reason  can  you 
give  for  thinking  that  the  direction  of  river  flow  is  a  consequence 
of  (or  is  consequent  upon)  the  slope  of  the  plain  ?    NOTE  :  Rivers 
whose  general  course  has  been  determined  by  the  original  (or  initial) 
slope  of  the  land,  as  given  by  uplift,  may  be  classed  as  consequent 
rivers;  the  valleys  of  such  rivers  may  be  classed  as  consequent  val- 
leys.   3.  4  3  is  a  profile  across  the  plain  from  the  oldland  to  the 
sea.    The  broken  line  L'R'F'  indicates  parts  of  the  river  (and  valley 
floor)  of  4  2  (or  4 1).    4.  Complete  the  broken  line  by  a  [blue]  line, 
and  prolong  it  to  the  sea.    5.  Why  is  the  valley  deeper  at  F'  than 
at  E'  ?    6.  How  do  you  suppose  the  valley  was  formed  ?    7.  What 
controls  the  depth  to  which  the  valley  can  be  eroded  ?    (DE,  145.8, 
254.1-7;   DP,  120.5;    T,  55.8.)     (Use  the  term  baselevel  in  your 
answer.)    8.  How  is  the  baselevel  of  the  plain  indicated  in  43? 
9.  Was  the  valley  formerly  deeper  or  less  deep  than  now  ?    10.  Can 


20  EXERCISES  IN  PHYSICAL   GEOGRAPHY 

the  depth  of  the  valley  be  much  more  increased  at  E'  ?  at  V  ? 
11.  What  is  the  average  fall  per  mile  of  the  oldland  slope  ?  of 
the  coastal  plain  ?  of  the  river  from  .F  to  the  sea  ?  12.  Which  is 
the  steepest  ?  least  steep  ?  Why  ?  NOTE  :  Most  coastal  plains  are 
much  broader  than  those  here  shown ;  the  slope  of  their  surface 
toward  the  ocean  is  often  extremely  gentle  and  may  be  less  regular 
than  it  is  indicated  in  the  diagrams  of  this  exercise.  13.  What 
effect  would  this  have  on  the  straightness  or  crookedness  of  conse- 
quent rivers  across  such  plains  ?  14.  To  what  class  do  the  streams 
on  the  coastal  plain  of  6  15  belong  ?  15.  Is  their  direction  of  flow 
as  regular  as  that  of  the  stream  in  4  2  ?  Explain. 

4.  [1.  What  reason  can  be  found  in  4  1  or  42  for  saying,  "The 
river  has  (practically)  ceased  deepening  its  valley  from  F  to  the 
ocean  "  ?  in  4  2  (or  6  14)  for  saying,  "  The  river  is  still  (actively) 
deepening  its  valley  in  the  part  upstream  from  F"?  2.  Why  has 
the  river  not  worn  down  its  course  between  F  and  the  ocean  to  a 
gentler  slope,  and  thus  given  that  part  of  its  valley  a  greater  depth? 
[The  following  questions,  3-8,  will  aid  in  answering  the  preceding 
one.  3.  If  a  river  has  no  slope,  what  velocity  can  it  have  ?  4.  If 
it  has  no  velocity,  how  much  rainfall  can  it  discharge  from  its  drain- 
age basin,  and  how  much  land  waste  (gravel,  sand,  silt)  can  it  sweep 
along  or  transport  ?  5.  The  river  here  considered  may  have  head- 
waters like  those  of  1 1.  Will  it  or  will  it  not  have  some  rainfall  to 
discharge,  and  some  load  to  transport  in  its  lower  course  ?  6.  Must 
it  then  still  have  some  slope  near  its  mouth  ?  7.  Explain  the  state- 
ments :  "When  a  river  has  a  greater  velocity  than  is  needed  in 
transporting  its  load  of  waste,  it  will  erode  its  bed  (valley  bottom) 
and  thus  lessen  its  slope  and  decrease  its  velocity";  "A  river  can- 
not erode  its  bed  to  so  small  a  slope  as  to  lose  the  velocity  needed 
in  transporting  its  load  of  waste."  8.  To  what  parts  of  4  2  do  these 
statements  apply  ?]  9.  How  can  the  term  graded  river  be  used  in 
this  connection  ?  (DE,  254.1  ;  DP,  237.6  ;  T,  56.9.)  10.  Which  parts 
of  the  river  in  42  are  already  graded  ?  not  yet  graded?  11.  Answer 
the  same  questions  (as  well  as  you  can)  for  the  rivers  V  and  F,  1 1. J 


VALLEYS  IN  A  COASTAL  PLAIN  21 

5.  [1.  When  the  valley  sides  are  examined  closely  near  the  inner 
border  of  a  coastal  plain,  such  as  is  shown  in  the  small  block  dia- 
gram, 6  14  (larger  scale  than  4  1),  the  hard  rocks  of  the  oldland 
are  seen  to  extend  a  moderate  distance  down  the  valley,  under  the 
overlapping  layers,  or  strata,  of  the  coastal  plain.  2.  Draw  a  [red] 
line  on  the  valley  side  of  6 14  separating  the  coastal-plain  strata 
from  the  underlying  extension  of  the  oldland  rocks.  3.  Is  this 
line  horizontal  or  sloping  ?  4.  Compare  its  slope  with  the  slope  of 
the  river  ;  of  the  coastal  plain.  NOTE  :  The  underground  exten- 
sion of  the  oldland  rocks  usually  has  a  surface  of  much  less 
slope  than  is  here  shown.  5.  Draw  broken  [red]  lines  along  the 
valley  side  to  show  the  edges,  or  outcrops,  of  the  coastal-plain 
strata  there  exposed.  6.  Do  the  coastal-plain  strata  slope  toward 
the  oldland  or  toward  the  ocean  ?  7.  Does  their  total  thickness 
increase  toward  the  oldland  or  toward  the  ocean  ?  8.  Can  the 
sfriu-ture  (arrangement  and  composition  of  layers,  etc.)  of  a  coastal 
plain  be  better  studied  in  a  district  without  valleys,  like  3  1  of 
Exercise  II,  or  along  the  valley  sides  of  a  district  like  that  of  4  2  (or 
6  14)  of  this  exercise  ?  Why  ?  9.  What  is  the  structure  of  a  coastal 
plain  ?  10.  What  is  the  relation  of  the  uppermost  layer  to  the 
original  siirface  of  the  plain  ?  11.  Draw  in  6  14  some  [red]  hachure 
lines  on  the  E.  side  of  the  valley  at  A,  B,  and  C.  12.  Which  ones  of 
these  lines  have  a  steeper  slope  near  the  bottom  than  near  the  top  ? 
Why  ?  13.  Why  is  the  valley  so  much  narrower  and  less  deep  at 
A  than  at  B  ?  14.  In  4  3  what  is  the  average  fall  per  mile  of  the 
river  from  F'  to  the  mouth  ?  from  V  to  F'  ?  15.  Which  part  is 
steeper  ?  Why  ?  16.  In  which  part  do  cascades  and  rapids  occur  ? 
17.  Which  part  could  be  most  easily  followed  by  boats  ?  18.  Sup- 
pose that  all  the  rivers  which  cross  this  coastal  plain  are  like  the 
river  of  4  2,  and  imagine  a  line  drawn  through  all  the  points  hav- 
ing a  position  similar  to  R.  19.  Will  this  line  lie  near  the  inner 
or  the  outer  border  of  the  plain  ?  20.  Why  may  it  be  called  the 
fall  line  ?  (DE,  157.1 ;  DP,  127.8  ;  G,  70.8  ;  T,  75.1.)  21.  What 
is  the  relative  direction  of  the  fall  line  and  the  shore  line? 


22  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

22.  How  is  the  fall  line  related  to  the  "head  of  navigation"  (the 
point  farthest  upstream  which  can  be  reached  by  boats  from  the 
sea)  ?  to  the  situation  of  villages  or  cities  that  make  use  of  water 
power  in  manufacturing  ?  23.  Name  several  cities  of  this  kind  in 
the  eastern  United  States.  (DE,  158.2 ;  DP,  128.9 ;  T,  75.6.) 
[24.  Examine  Rocky  river,  35  1,  near  Berea.  At  what  point  does 
it  show  a  rapid  fall  ?  What  is  the  (probable)  origin  of  this  fall  ? 
What  use  may  be  made  of  it  in  Berea?  25.  What  evidence  does  the 
river  give  of  being  graded  from  the  fall  to  lake  Erie  ?  What  is 
its  slope  in  its  graded  course  ?  How  much  does  it  fall  at  Berea  ? 
26.  Compare  the  depth  of  the  valley  beneath  the  plain,  upstream 
and  downstream  from  the  fall  ;  explain  the  difference.] 

6.  If  §  5  is  omitted,  omit  §  6  also.    [1.  Suppose  that  a  deep  well 
at  D,  4  2,  reaches  hard  rocks,  like  those  of  the  oldland,  at  a  depth 
of  25' ;  a  well  at  C  reaches  them  at  35' ;  one  at  M,  at  50'  below 
the  surface  of  the  plain.    2.  What  does  this  indicate  as  to  the  gen- 
eral slope  of  the  ancient  sea  bottom  on  which  the  coastal-plain  strata 
were  laid  down  ?    3.  Draw  a  (gently  undulating)  line  in  4  3  to  repre- 
sent the  profile  of  the  ancient  sea  bottom.    4.  At  what  depth  below 
the  surface  of  the  plain  at  K,  4  2,  would  the  hard  rocks  probably 
be  reached  in  a  well?    5.  How  a-re  the  hard  rocks  of  the  oldland 
and  the  strata  of  the  coastal  plain  represented  on  the  W.  and  S. 
faces  of  the  block  diagram,  6 14  ?    6.  Why  are  the  coastal-plain 
strata  drawn  slanting  on  the  left  side  of  the  block  and  horizontal 
on  the  front  face  ?    7.  What  facts,  observed  on  the  valley  sides, 
or  discovered  in  deep  wells,  give  reason  for  shading  the  block 
faces  in  this  way  ?    8.  State  the  relation  of  the  facts  presented  in 
this  section  to  artesian  wells.    (DE,  238.1 ;  DP,  126.8 ;    G,  154.3 ; 
T,  72.9.)    NOTE  :   The  relation  of  artesian  wells   to  the  Atlantic 
coastal  plain  of  the  United  States  is  fully  treated  by  N.  H.  Darton, 
Bulletin  138,  U.  S.  G.  S.] 

7.  1.  Mark  the  river  [red]  where  it  is  flowing  against  the  valley 
sides  in  4 1  ?    in  4 1  a  ?  in  4  2  ?  in  5  8  ?    2.  At  such  places  the  base 
of  the  valley  side  is  worn  away  by  the  river,  and  as  a  result  the 


VALLEYS  IN  A  COASTAL  PLAIN  23 

loose  waste  on  the  valley  side  slips  down  into  the  river  and  is 
washed  away.  3.  What  effect  will  this  have  on  the  width  of  the 
valley  floor  ?  Explain  by  the  left  slope  of  4  4.  (This  figure  is  a 
cross  profile  of  a  valley ;  it  is  on  a  larger  scale  than  4  2.)  4.  Where 
is  the  waste  from  the  valley  sides  finally  deposited  ?  5.  The  river 
slowly  changes  its  course,  now  undercutting  this  part,  now  that 
part,  of  the  valley  sides.  What  effect  will  this  have  on  the  width 
of  the  valley  as  a  whole  ?  6.  Was  the  valley  formerly  narrower  or 
wider  than  now  ?  7.  What  relation  must  exist  between  the  altitude 
of  the  plain  (as  determined  by  amount  of  uplift)  and  the  depth  of 
its  valleys  ?  between  the  age  of  the  plain  (time  since  its  slow 
uplift)  and  the  width  of  its  valleys  ?  8.  Mark  x  on  5  8  and  on 
4  1,  where  cities  might  be  built  on  the  upland  close  to  the  river,  so 
as  to  have  the  advantage  of  trade  by  river  boats,  and  to  avoid  the 
danger  of  river  floods.  9.  What  cities  are  thus  situated  with 
respect  to  the  Mississippi  river?  (See  5  8 a,  5  8ft.)  On  which  side  of 
the  river  and  in  what  states  are  these  cities  ? 

8.  1.  Draw  in  4  5  an  E.-W.  profile  across  the  valley  of  4  2  at  DFD'. 
(Determine  the  altitude  of  the  plain  and  of  the  valley  floor  on  the 
line  DFD'  in  4  2  ;  mark  on  edge  of  paper  slip  the  breadth  of  valley 
at  top  and  at  bottom  of  the  side  slopes  ;  transfer  to  4  5.)  2.  Add 
dotted  lines  to  4  5  to  show  two  earlier  cross  profiles  and  two  later 
cross  profiles.  3.  Which  will  be  greater  in  future,  the  deepening 
or  the  widening  of  the  valley?  Why  ?  4.  Part  of  a  similar  valley 
is  mapped  in  3  6d :  the  valley  sides  are  shaded  with  down-slope  lines 
or  hachures  ;  the  unworn  upland  is  dotted.  5.  Complete  3  6  c  and 
3  6  e,  to  show  earlier  and  later  stages  of  valley  form  ;  complete  the 
other  figures  of  this  series.  6.  What  does  the  series  show  as  to 
change  in  curvature  of  river  ?  in  breadth  of  valley  floor?  in  upland 
area  ?  7.  On  which  is  erosion  more  rapid,  a  steep  valley  side  or  a 
nearly  level  upland  plain  ?  Why  ?  8.  A  valley  in  the  stage  of 
development  shown  ins6a  may  be  called  young;  in  the  stage  of 
36d,  mature.  9.  Why  are  these  terms  appropriate?  10.  In  what 
stage  of  development  is  the  valley  of  42  at  H?  11.  The  upland 


24  EXERCISES  IN  PHYSICAL   GEOGRAPHY 

plain  bordering  the  valley  of  3  6  d  has  been  very  little  changed  ; 
such  a  plain  may  therefore  be  described  as  in  a  young  stage  of 
development,  although  its  river  and  valley  are  mature.  12.  In 
what  stage  is  the  plain  mapped  in  4  7  ?  13.  In  what  stage  are  the 
valleys  of  4  7  ?  14.  What  are  the  most  important  elements  or 
parts  of  a  young  coastal  plain  ?  of  a  mature  valley  in  a  young 
coastal  plain  ?  [15.  What  are  the  variable  elements  of  a  young  coastal 
plain  ?  NOTE  :  The  form  of  the  oldland  may  vary  greatly  in  differ- 
ent examples  ;  it  is  sometimes  less,  sometimes  more  hilly  or  moun- 
tainous ;  its  border  may  be  nearly  straight,  moderately  curved,  or 
very  irregular,  etc.] 

9.  1.  Heavy  rain  may  wear  channels  or  gulleys  in  valley  sides. 
Why  ?    2.  What  becomes  of  the  waste  that  is  washed  from  the 
gulleys  ?    3.  As  time  passes,  the  gulleys  are  worn  back  farther  and 
farther  into  the  plain.    Why  ?    4.  As  the  gulleys  grow  to  a  length 
of  a  few  hundred  feet  or  more,  they  may  be  called  ravines.    5.  How 
many  ravines  are  shown  in  the  block  diagram,  58?     (Scale  much 
larger  than  in  4  1.)    6.  Draw  in  5  8  [red]  lines  along  the  100'  and 
150'  contours  on  the  farther  side  of  the  valley.    7.  Why  do  the  con- 
tours turn  from  the  valley  side  into  the  ravine  ?    8.  How  do  the 
contours  turn  where  they  cross  the  ravine  stream  (or  rivulet)?  9.  5  9 
is  a  map  (on  still  a  larger  scale).    Which  part  of  5  8  does  it  show  ? 
Draw  the  100'  and  150'  contours  in  the  ravine.     10.  How  do  the 
contour  lines  of  a  main-valley  side  turn  when  they  come  to  a  side 
ravine  ? 

10.  1.  5 10,  5 11,  5  12,  are  contour-line  maps  (except  that  ravine 
H  is  hachured)  representing  three  stages  in  the  development  of  a 
valley  and  its  ravines  in  a  coastal  plain  ;  the  scale  is  the  same  as 
in  4  2.    The  top  and  bottom  of  the  valley-side  slopes  are  shown  by 
dotted  lines.    2.  What  is  the  contour  interval  ?  the  altitude  of  the 
upland  and  the  depth  of  the  main  valley  at  the  N.  border  of  5 10  ? 
the  breadth  of  the  main  valley  floor  ?    3.  How  can  you  tell  which 
figure  represents  the  earliest  of  the  three  stages  ?  the  latest  of  the 
three  ?    4.  Draw  the  stream  for  ravine  R,  5  10 ;  draw  the  contours 


VALLEYS  IN  A  COASTAL  PLAIN  25 

for  ravine  Q.  5.  How  does  ravine  T  differ  from  ravine  R  as  to 
length  ?  as  to  branches  (or  forks)  ?  6.  Add  a  line  on  the  left  side 
of  the  valley  in  4  4  to  show  the  profile  of  a  short  ravine  stream. 
7.  Which  has  the  steeper  fall,  a  ravine  stream  or  the  river  that  it 
flows  into  ?  Why?  8.  Compare  ravine  T  in  5  10,  5  11,  and  5  12  as 
to  length  ;  as  to  branches.  9.  How  are  the  changes  produced  ? 
10.  Compare  the  direction  in  which  the  ravine  is  lengthened  with 
the  direction  of  its  stream  flow.  Explain.  11.  How  can  the  term 
he«dward  erosion  [or  retrogressive  erosion]  be  used  in  this  connec- 
tion ?  12.  As  the  ravines  gain  the  length  of  a  mile  or  two  they  may 
be  called  side  valleys  ;  the  parts  of  the  upland  that  enter  between 
ravine  or  valley  branches  may  be  called  spurs.  13.  By  what  letter 
are  some  of  the  spurs  E.  of  the  main  valley  indicated  in  5  11  and  5  12? 
Print  the  same  letter  on  four  other  spurs.  14.  In  which  figure  are 
upland  spurs  most  numerous  ?  Why  ?  15.  Draw  in  5  11  and  5  12 
the  contoiirs  for  ravine  Q,  beginning  with  the  50'  contour.  Draw  the 
stream  (and  its  branches)  for  ravine  R.  16.  Add  to  the  left  side  of 
4  4  two  side-stream  profiles  later  than  the  one  previously  drawn ; 
on  the  latest  profile  draw  also  the  profile  of  a  branching  rivulet. 
17.  Which  valley,  5  10,  a  11,  or  5  12,  most  nearly  corresponds  in 
stage  of  development  to  the  valley  of  Rocky  river,  35  1.  [18.  Many 
of  the  side  streams  and  valleys  in  5  12  are  somewhat  irregular  in 
direction,  but  most  of  the  larger  ones  (almost)  agree  in  direction 
with  the  general  slope  of  the  plain.  Why  do  they  thus  (almost) 
agree  ?  19.  To  what  class  do  they  belong  ?  (See  §  3  of  this  exercise.) 
Why?  20.  The  streams  and  valleys  whose  direction  is  less  regular 
may  be  called  insequent,  because  they  do  not  follow  the  general 
slope  of  the  plain.  Print  I N  near  some  insequent  ravines  in  5  12. 
21.  The  fainter  the  initial  slope  of  the  plain  the  more  numerous 
and  irregular  will  be  the  insequent  streams.  Why  ?] 

11.  1.  What  is  the  width  of  the  main  valley  floor  in  5  10,  5  11, 
and  5  12?  What  change  is  shown?  How  has  it  been  produced? 
[2.  Why  has  the  depth  of  the  main  valley  not  changed  ?  3.  In 
what  direction  (compared  to  the  general  direction  of  the  river)  has 


26  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

the  bend  W  in  the  main  river  shifted  its  position  in  the  change 
from  5  10  to  5  11?  from  5 11  to  5  12  ?  4.  Have  the  other  bends 
shifted  in  the  same  way  ?]  5.  Why  may  the  river  and  valley  of 
5  11  be  called  mature  ?  6.  Suppose  that  the  next  river  valley  E. 
of  5  12  to  be  a  mile  away ;  describe  the  features  that  you  would 
pass  in  walking  from  one  river  to  the  other.  7.  Which  parts  of  the 
upland  plain  might  be  described  as  dissected  by  ravines  ?  Which 
part  as  undissected,  or  as  not  yet  dissected?  8.  What  becomes  of  the 
rain  which  falls  on  the  undissected  parts  ?  9.  In  which  of  these 
parts  would  roads  be  straight  ?  crooked  ?  Why  ?  In  which  parts 
would  plowing  and  reaping  be  easiest  ?  Why  ?  10.  Which  parts 
would  probably  be  cultivated?  Which  parts  left  to  be  overgrown 
with  bushes  and  trees  ?  11.  Which  parts  of  a  coastal  plain  (in  re- 
lation to  its  main  consequent  rivers)  will  be  earliest  dissected  ? 
latest  dissected  ?  12.  Upon  what  factors  will  the  depth  of  dissec- 
tion (strength  of  relief)  depend  ?  13.  When  so  many  branching 
side  valleys  have  been  formed  that  little  of  the  plain  remains  undis- 
sected, why  may  it  be  described  as  maturely  dissected,  or  as  hav- 
ing reached  a  mature  stage  in  its  cycle  of  erosion?  14.  Which 
reaches  maturity  first,  the  upland  of  a  coastal  plain  or  a  large  con- 
sequent river  which  crosses  it  ?  WThy  ?  15.  Why  may  the  upland 
surface  of  a  young  coastal  plain  be  described  as  undivided,  or  as 
indistinctly  divided  as  to  stream  basins  ?  16.  Why  may  the  up- 
land surface  of  a  mature  coastal  plain  be  described  as  thoroughly 
subdivided  as  to  stream  basins  ?  [17.  Describe  the  appearance  of  a 
district  80  mi.  inland  in  a  mature  coastal  plain  in  which  the  initial 
surface  had  a  seaward  slope  of  5'  in  a  mile,  this  district  extending 
between  two  large  consequent  rivers,  10  mi.  apart,  each  having  a 
fall  of  6"  in  a  mile.  18.  WThat  changes  in  relief  would  be  noted  in 
crossing  this  district  from  one  of  the  rivers  to  the  other  ?  in  going 
from  the  middle  of  the  district  to  the  seashore  ?] 

12.  1.  In  what  direction  does  the  coastal  plain  of  6  13  slope  ? 
About  how  wide  is  it  ?  About  how  high  along  its  inner  border?  What 
is  its  slope  in  feet  per  mile?  [2.  Draw  in  o!3a  a  cross  profile  of 


27 

this  plain,  and  indicate  the  extension  of  the  oldland  rocks  beneath 
the  strata  of  the  plain.]  3.  How  many  consequent  rivers  cross  the 
plain  from,  the  oldland  ?  4.  What  is  their  average  fall  per  mile  ? 
5.  Draw  several  branching  streams,  as  indicated  by  the  contour 
lines.  [6.  Are  the  branch  streams  mostly  consequent  or  insequent  ?] 
7.  Mark  S  on  some  spurs  between  the  stream  valleys.  8.  Is  this 
plain  in  an  earlier  or  a  later  stage  of  development  than  the  plain 
of  4  7  ?  How  can  you  tell  ?  9.  In  what  stage  is  each  plain  ? 
State  your  answers  in  such  terms  as  early  youth,  late  youth,  early 
maturity,  full  maturity,  late  maturity.  10.  Suppose  the  region 
of  6  13  to  be  lowered,  or  depressed,  110' ;  draw  a  [blue]  line  to 
show  the  shore  line  after  depression.  11.  Why  is  the  new  shore 
line  irregular?  12.  What  is  the  relation  of  valleys  and  spurs  of 
the  plain  before  depression  to  bays  and  land-points  of  the  shore 
line  after  depression  ?  13.  Why  do  some  bays  reach  farther  inland 
than  others  ?  14.  Why  may  these  narrow  bays  be  described  as 
partly  drowned  valleys  ?  15.  Why  may  the  shore  line  be  described 
as  embayed?  16.  Would  the  water  in  the  bays  be  salt  or  brack- 
ish ?  NOTE  :  At  the  head  of  a  long  narrow  bay,  into  which  a  large 
river  flows,  the  water  may  be  partly  salt  or  brackish.  17.  Narrow 
bays  of  this  kind  are  sometimes  called  "  rivers."  How  do  such 
"rivers"  differ  from  ordinary  rivers  ?  18.  May  the  name  "river" 
be  properly  given  to  the  water  that  occupies  a  (partly)  drowned 
valley?  [19.  Suppose  the  region  of  5 12  to  be  depressed  75' ;  draw 
the  new  shore  line  [blue],  and  shade  lightly  [blue]  the  submerged 
or  drowned  parts.  20.  About  how  deep  would  the  chief  bay  be  at 
Y  ?]  [21.  If  an  explorer  came  upon  a  coastal  plain,  what  features 
should  he  examine  in  order  to  give  a  good  account  of  it  ?] 

13.  [1.  Part  of  the  Atlantic  coastal  plain  of  the  Eastern  United 
States  is  shown  in  352.  Locate  it  on  Plate  40.  2.  What  is  the 
scale  of  the  map  ?  the  contour  interval  ?  the  altitude  of  the  upland 
above  sea  level  ?  the  depth  of  Trent  river  valley  below  the  upland 
plain  ?  3.  This  part  of  the  plain  is  25  mi.  inland  from  (W.  of)  the 
Atlantic  shore  line.  What  is  the  average  slope  of  the  plain  ?  the 


28  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

average  fall  of  Trent  river  (distance  along  river  course  to  mouth 
about  38  mi.)  ?  4.  With  which  figure  of  3  6a-6ff  does  the  Trent 
valley  best  correspond  ?  5.  In  what  stage  of  development  is  this 
valley  ?  6.  Is  the  plain  much  dissected  or  little  dissected  ?  In  what 
stage  of  development  is  the  plain  ?  7.  Another  part  of  the  Atlantic 
coastal  plain  in  North  Carolina  is  shown  in  35  3.  What  is  the  scale  ? 
the  contour  interval  ?  8.  What  is  the  general  altitude  of  the  up- 
land above  sea  level  ?  the  general  depth  of  the  valleys  below  the 
upland?  9.  About  how  wide  are  the  valley  floors  or  flood  plains? 
10.  What  features  of  this  district  show  it  to  be  in  a  more  or  less 
advanced  stage  of  development  than  the  preceding  example  ?  11.  In 
what  stage  of  development  are  the  streams  and  valleys  ?  the 
uplands  ?  12.  A  third  part  of  the  Atlantic  coastal  plain  is  shown 
in  35  4.  Locate  it.  What  is  the  scale  of  the  map  ?  the  contour 
interval  ?  13.  What  is  the  general  altitude  of  the  uplands  ?  the 
depth  of  the  valleys  ?  14.  In  what  stage  of  development  is  this 
part  of  the  coastal  plain  ?  15.  What  movement  (elevation  or 
depression)  appears  to  have  taken  place  since  the  dissection  of  the 
plain  ?  16.  How  wide  is  Wicdmico  "  river  "  ?  17.  How  do  you  sup- 
pose it  gained  so  great  a  width  ?  18.  Do  you  think  that  the  water 
of  this  "river"  is  fresh,  salt,  or  brackish?  19.  Is  the  Wicdmico 
properly  a  river  or  a  narrow  bay  ?  20.  Compare  the  location  of 
the  villages,  Wicdmico  and  Chaptico. 

14.  Define  the  following  terms :  Preliminary  §,  flood  plain  ; 
§  3,  consequent  river,  consequent  valley,  baselevel  ;  [§  4,  graded 
river  ;  §  5,  outcrop,  structure,  fall  line  ;  §  6,  artesian  well  ;]  §  8,  young 
valley,  mature  valley,  young  coastal  plain  ;  §  9,  gulley,  ravine  ; 
§  10,  side  valleys,  headward  erosion  [retrogressive  erosion],  spur, 
[insequent  stream] ;  §  11,  late  mature  valley,  dissected  plain, 
maturely  dissected  plain;  §  12,  drowned  valley,  embayed  shore 
line. 


EXEECISE  IV.   PLATEAUS  AND  CANYONS 

OBJECT.   To  study  the  forms  produced  by  the  erosion  of  a  plateau. 

Preliminary.  7  1  is  drawn  as  if  a  block  of  the  earth's  crust  had 
been  cut  out  from  a  plateau,  through  which  a  river  flows  at  the 
bottom  of  a  canyon,  or  deep  and  narrow  valley.  The  block  shows 
a  vertical  front  face,  as  MNRQ.  The  figure  is  drawn  as  if  in  a 
desert,  free  from  vegetation,  so  as  to  show  its  forms  better.  Hori- 
zontal and  vertical  scales  are  the  same.  North  is  toward  the  back 
of  the  block  ;  the  back  is  (about)  two  miles  from  the  front.  The 
base  of  the  block  represents  sea  level.  Distances  E.  and  W.  (right 
and  left)  may  be  measured  on  the  scale  of  miles  at  the  front  base 
of  the  block;  altitudes,  on  the  vertical  scales  (broken  lines)  that 
rise  through  the  river  in  the  foreground  and  background.  The  left 
front  profile  is  omitted,  so  that  it  may  be  drawn  by  the  pupil. 
The  plateau  must  be  thought  of  as  extending  a  long  distance  in 
all  directions.  The  beginning  of  the  canyon  is  many  miles  N.  ;  the 
end,  many  miles  S.  of  the  part  here  drawn.  This  exercise  uses 
7,  8,  9,  10,  1-10 ;  [also  36  1-5]. 

1.  1.  How  many  vertical  rock  faces  or  cliffs  are  seen  in  7 1  on  the 
E.  side  of  the  canyon  ?  on  the  W.  side  ?  2.  How  many  inclined 
slopes  on  each  side  ?  3.  Compare  the  cliffs  on  the  two  sides  as 
to  height ;  compare  the  slopes  on  the  two  sides  as  to  down-slope 
length.  4.  What  is  the  altitude  (above  sea  level)  of  the  top  of 
cliff  D  in  the  foreground  (use  the  foreground  vertical  scale)  ?  in 
the  background  (use  the  background  vertical  scale)  ?  of  the  top 
of  cliff  B  in  the  foreground  and  background  ?  5.  Where  on  the  W. 
side  of  the  canyon  do  you  see  a  group  of  rock  layers,  or  strata,  cor- 
responding to  the  group  which  appears  or  outcrops  in  cliff  D  on  the 
E.  side  ?  in  cliff  B  ?  6.  Compare  the  altitude  of  the  corresponding 

29 


30  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

cliff  tops  on  the  two  sides  of  the  canyon.  [Make  a  rough  imitation 
of  a  plateau  and  canyon  with  two  piles  of  books.]  7.  Are  the  strata 
of  cliff  D  in  a  horizontal  or  a  slanting  (inclined)  attitude  ?  of 
cliff  B  ?  8.  Draw  some  light  lines  on  the  front  face  of  7  1  to  show 
the  attitude  of  the  slope-making  strata.  9.  Describe  the  structure 
(arrangement  and  composition  of  the  strata)  of  the  plateau.  (DE, 
162.8;  DP,  141.2;  G,  175.2;  T,  82.9.) 

2.  1.  Suppose  that,  at  time  of  rain,  a  small  stream  ran  forward 
past  X,  7  1,  to  the  rim  of  the  plateau  and  fell  from  the  cliff ;  draw 
a  [blue]  line  to  show  its  path  down  to  the  river.    2.  Compare  this 
line  with  the  profile  of  the  E.  canyon  wall  on  the  front  face  of  the 
block.    3.  What  is  the  (vertical)  thickness  of  the  group  of  strata,  or 
formation,  which  determine  cliff  D  ?  cliff  B  ?  slope  C  ?  NOTE  :  Weak 
strata  crumble  away,  forming  slopes  ;  strong  or  resistant  strata  pre- 
serve steep  cliff  faces  for  a  long  time.    4.  Complete  the  front  profile 
on  the  W.  side  of  the  canyon  (making  it  correspond  to  the  E.  side)  ; 
shade  lightly  [or  tint  with  crayons]  the  strong  formations,  or  cliff 
makers,  for  an  inch  or  more  to  the  left  of  the  W.  profile.    5.  Print 
letters  on  the  cliff-making  and  slope-making  formations,  in  the  front 
section,  E.  and  W.  of  the  canyon,  corresponding  to  the  letters  A—D 
on  the  canyon  wall.    6.  What  is  the  relation  between  the  height  of 
a  cliff  face  (from  bottom  to  top)  and  the  thickness  of  the  cliff-making 
formation  ?  between  the  length  of  a   slope   (measured  along   its 
incline)  and  the  vertical  thickness  of  its  weak  formation  ?    7.  Is 
the  uppermost  formation  E  strong  or  weak? 

3.  1.  What  is  the  general  altitude  of  the  plateau  surface  in  7  1  ? 
2.  Fossils  of  marine  animals  are  often  found  in  the  strata  of  which 
plateaus,  such  as  the  one  here  figured,  are  built.    Under  what  con- 
ditions must  such  strata  have  been  deposited  ?    3.  What  movement 
of  the  earth's  crust  must  be  supposed  in  the  plateau  region,  since 
the  strata  were  deposited  ?    4.  What  is  the  depth  of  the  canyon 
beneath  the  plateau  surface  at  the  back  of  7  1  ?    at  the  front  ? 
5.  Which  way  does  the  river  flow  ?    6.  On  what  formation  is  the 
river  flowing  in  the  background  ?  In  what  formation  is  it  flowing 


PLATEAUS  AND  CANYONS  31 

for  most  of  its  length  in  7  1  ?  7.  To  what  parts  of  7  1  do  the  rapids, 
falls,  and  lower  course  of  the  river  in  7  la  correspond  ?  8.  Draw  in 
7  1  a  the  profile  of  the  rapids  and  falls  when  the  cliff  of  the  falls 
stood  1000'  farther  S.  (use  the  horizontal  scale  of  7  1)  ;  when  the 
cliff  comes  to  stand  500'  farther  1ST.  9.  Describe  how  the  retreat 
or  recession  of  the  falls  is  brought  about.  (DE,  251.8 ;  DP,  144.2, 
235.8;  (,',  41.2;  7',  54.2.)  10.  How  do  you  suppose  the  canyon  was 
formed?  (DK,  162.7;  DP,  141.9;  G,  32.1;  T,  81.4.)  11.  What  is 
the  width  of  the  river  ?  of  the  canyon  at  the  level  of  the  river  in 
the  foreground  ?  of  the  canyon  at  the  level  of  the  plateau  (top  of 
cliff  Z>)  in  the  foreground  ?  12.  Why  is  the  canyon  wider  at  the 
top  than  at  the  bottom  ?  13.  Draw  two  vertical  lines  in  the  front 
of  7  1  to  show  the  form  that  the  canyon  would  have  had  if  the 
strata  in  its  walls  had  not  weathered  and  crumbled  (that  is,  as  if 
the  canyon  had  been  cut  only  by  the  river).  14.  In  the  canyon 
as  drawn  in  7  1,  has  the  greater  amount  of  rock  been  eroded  by  the 
direct  action  of  the  river  or  by  the  action  of  weather  on  the  walls  ? 
4.  1.  What  effect  will  the  (relatively)  rapid  weathering  and 
wasting  of  formation  C,  1  1,  have  on  its  sloping  face  ?  on  the  face 
of  the  slow-weathering  cliff  D  ?  Answer  the  same  questions  for 
formations  A  and  B.  2.  How  may  the  term  retreat  or  recession 
be  used  in  this  connection  ?  3.  Draw  a  line  W.  of  the  canyon, 
showing  the  profile  of  its  wall  after  cliff  D  has  retreated  200'. 
4.  What  becomes  of  the  large  rock  blocks  that,  from  time  to  time, 
may  be  loosened  by  the  weathering  of  cliff  D  ?  5.  Why  is  not  the 
bottom  of  the  canyon  heavily  filled  with  waste  that  has  fallen  from 
its  walls  ?  6.  What  relation  must  exist  between  the  supply  of  waste 
from  the  walls  and  the  load  of  waste  that  the  river  can  transport  ? 
7.  In  order  to  wash  away  or  transport  the  waste  that  falls  from  the 
canyon  walls,  must  the  river  have  a  rapid  or  a  slow  current  ?  a 
strong  or  faint  slope  ?  NOTE  :  Some  of  the  waste  from  each  cliff 
remains  on  the  slope  below  it,  and  (with  the  finer  waste  from  the 
slope-making  formation)  makes  a  cover  or  talus  on  the  slope. 
Weathering  causes  the  talus  fragments  to  creep  slowly  down  the 


32  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

slope  ;  washing  hastens  their  movement.  8.  What  becomes  of  the 
talus  waste  in  7  1  when  it  reaches  the  foot  of  slope  C  ?  of  slope 
A  ?  9.  Which  parts  of  the  walls  show  the  greatest  amount  of  bare 
rock  outcrops  ?  Which  parts,  the  least  ?  Why  ?  10.  Do  the  weak 
or  strong  formations  show  the  best  outcrops  ? 

5.  1.  How  does  the  cross  profile  of  the  canyon  in  the  background 
of  7  1  differ  in  depth  and  width  from  the  cross  profile  in  the  fore- 
ground?   2.  Draw  in  the  background  (see  dotted  line  f/f/)  a  cross 
profile,  as  if  to  show  the  canyon  some  miles  upstream  ;  another  cross 
profile  (see  dotted  line  VV")  still  farther  upstream.    How  do  the 
depth  and  width  of  the  canyon  change,  as  it  is  followed  upstream  ? 
3.  What  will  be  the  position  of  the  river,  still  farther  upstream, 
in  relation  to  formation  D  ?    4.  Draw  a  profile  along  that  part  of 
the  river  to  show  this  relation  (part  of  formation  D  on  the  left  front 
face  of  7  1  may  be  used  in  drawing  this  profile).    5.  In  the  back- 
ground of  7  1  draw  a  profile  across  the  river  beyond  (N/.  of)  the  point 
where  it  falls  from  formation  D.  6.  How  is  that  part  of  the  river 
course  related  to  the  plateau  surface  ?    7.  Why  do  the  strong  (or 
resistant)  formations  deserve  the  name  of  "  cliff  makers  "  in  relation 
to  the  canyon  walls,  and  "  fall  makers "  in  relation  to  the  river 
course  ?    8.  In  which  kind  of  formation,  strong  or  weak  (resistant 
or  yielding),  does  the  greater  part  of  the  river  course  lie  ?    9.  In 
which  kind  of  formation  has  the  river  course  a  gentle  fall  ?  a  steep 
fall  ?    [10.  Estimate  the  fall  of  the  river  (feet  per  mile)  from  the 
foot  of  the  B  falls  to  the  foreground.] 

6.  1.  Suppose  you  were  at  Q,  1 1,  and  wished  to  go  to  M  without 
descending  into  and  climbing  out  of  the  canyon  ;  describe  the  route 
you  might  follow.    2.  Draw  in  the  foreground  a  cross  profile  (see 
dotted  line  W,  E.  of  canyon)  of  the  canyon  for  a  point  some  miles 
downstream  (assuming  the  altitude  of  the  plateau  to  continue  un- 
changed).   3.  How  does  profile  W  differ  in  depth  and  width  from 
the  foreground  profile  of  7  1  ?     How  does  profile  W  differ  from 
profile  F?    4.  How  do  the  depth  and  width  of  a  canyon  vary  as  it 
is  followed  downstream  ?    Explain.     [5.  What  limits  the  depth  to 


PLATEAUS  AND   CANYONS  33 

which  a  canyon  can  be  cut  ?  (Consider,  in  your  answer,  altitude  of 
plateau,  slope  of  river,  and  distance  from  the  river  mouth.)]  G.  What 
changes  in  depth  and  breadth  would  you  expect  at  the  front  profile 
of  7  1  if  weathering  and  river  action  continued  for  a  long  time  ? 
Why  have  these  changes  not  already  taken  place  ?  7.  Would  you 
describe  the  river  and  canyon  as  young,  mature,  or  old?  Why? 
8.  What  stage  in  the  cycle  of  erosion  do  you  think  the  plateau  has 
reached  ?  9.  What  are  the  chief  characteristics  of  a  young  plateau  ? 
[10.  The  Zambezi  river  in  the  interior  of  South  Africa  (locate  the 
river  on  Plate  45)  flows  in  a  broad  channel  with  a  moderate  current 
on  a  plateau  (altitude,  3500'),  following  a  broad  and  shallow  valley 
for  many  miles ;  it  then  suddenly  plunges  down  300'  at  Victoria 
Falls  into  a  narrow  and  steep-walled  gorge  or  canyon,  through  which 
it  rushes  rapidly  in  a  narrow  channel.  The  canyon  continues  40 
mi. ;  it  deepens  and  widens  (and  its  side  canyons  increase  in 
length)  as  it  is  followed  downstream  from  the  falls.  11.  What  is 
the  origin  of  the  canyon  ?  of  the  falls  ?  (See  (London)  Geograph- 
ical Journal,  Vol.  XXV,  1905  ;  Vol.  XXIX,  1907;  excellent  plates.)] 
7.  1.  8  2  is  a  diagram  of  another  plateau  and  canyon  drawn  in 
the  same  way  as  7  1.  How  does  it  differ  from  7  1  as  to  altitude  of 
plateau  ?  altitude  of  river  in  foreground  ?  depth  of  canyon  below 
plateau  surface  ?  breadth  of  canyon  at  plateau  level  ?  amount  of 
original  plateau  uplift?  number  of  cliffs  and  of  slopes  in  canyon 
wall  ?  height  of  waterfall  in  river  (near  B)  ?  2.  Complete  the  front 
profile  W.  of  the  river  in  8  2  and  draw  lines  separating  the  cliff- 
making  and  slope-making  formations  ;  shade  lightly  the  cliff-making 
formations  W.  of  the  canyon;  print  letters  on  the  several  forma- 
tions corresponding  to  the  letters  on  the  canyon  wall.  3.  Has  the 
plateau  mass  a  horizontal  or  an  inclined  structure  ?  4.  Draw  two 
canyon-wall  profiles,  W,  X,  as  if  for  points  farther  downstream,  in 
the  E.  foreground ;  two,  U,  V,  as  if  for  points  farther  upstream,  in 
the  E.  background.  5.  Mark  Q  at  a  point  where  you  would  go  to 
get  a  good  view  up  the  canyon  if  you  were  on  the  E.  part  of  the 
plateau ;  Q'>  on  the  W.  part  for  a  view  down  the  canyon.  [6.  Do 


34  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

the  dots  in  these  circles  represent  (about)  the  size  of  a  man  or  of 
a  house  ?]  7.  What  is  the  width  of  the  canyon  at  the  level  of  layer 
H  in  the  foreground  ?  in  the  background  ?  at  the  place  of  greatest 
width  ?  8.  Why  does  the  width  vary  ?  9.  Why  does  the  E.  side 
canyon  fork  near  its  head  (F),  while  the  W.  side  canyon  does  not 
fork  at  its  head  (Z)?  10.  At  what  time  in  its  history  (earlier  or 
later  than  now)  would  the  E.  side  canyon  resemble  the  present  form 
of  the  W.  side  canyon  ?  When  would  the  W.  side  canyon  resemble 
the  present  form  of  the  E.  side  canyon  ?  Explain. 

8.  1.  Why  is  cliff  face  D,  8  2,  higher  (from  bottom  to  top  of  cliff) 
than  cliff  face  F  ?  cliff  face  F  than  //  ?  [2.  Why  is  slope  G  less  steep 
than  slope  C  ?]  3.  Why  do  falls  occur  in  the  river  near  the  fore- 
ground ?  4.  If  you  could  follow  up  the  river,  would  the  next  fall 
probably  be  of  greater  or  of  less  height  than  the  one  here  shown  ? 
Why  ?  5.  How  many  falls  occur  on  the  (wet-weather)  stream  of 
the  E.  side  canyon  ?  of  the  W.  side  canyon  ?  Why  ?  (DE,  252.2  ; 
DP,  144.2;  G,  38.8;  T,  54.1.)  6.  Counting  down  from  the  plateau, 
which  fall  on  the  side  streams  will  be  the  highest  ?  7.  Draw  on 
the  W.  front  face  of  8  2  a  line  (beginning  at  the  river)  to  represent 
the  profile  of  the  W.  side  stream.  8.  AVhich  has  the  (average) 
steeper  descent,  a  side  stream  or  the  wall  of  the  main  canyon  ?  a 
side  stream  or  the  main  river  ?  Explain.  [9.  If  you  wished  to  de- 
scend from  the  plateau  to  the  river,  where  would  you  try  to  find  a 
way?  Why?  In  which  part  of  such  a  way  would  the  greatest  dif- 
ficulty be  found?  Why?]  [10.  Draw  (short)  horizontal  lines  to 
separate  the  strong  and  weak  formations  corresponding  to  the  profiles 
in  s2#  (the  profiles,  which  show  only  the  surface,  are  thus  changed 
into  sections,  which  show  also  the  internal  structure).  Shade  (lightly) 
the  cliff  makers  in  one  of  the  sections.  11.  Which  section  has  two 
thick  resistant  formations  ?  many  thin  resistant  formations  ?  a 
great  thickness  of  weak  strata  in  its  lower  part  ?  How  can  you 
tell  ?]  [12.  The  weaker  formations  are  sometimes  weathered  back 
a  few  feet  under  the  overlying  cliff-making  formation,  which  there- 
fore "overhangs,"  forming  natural  "cliff  caves."  8  2  a.  is  a  sketch 


PLATEAUS  AND  CANYOXS  35 

of  such  a  cave,  in  which  a  rough  wall  has  been  built  to  give 
better  protection.  Many  such  "cliff  dwellings,"  now  more  or  less 
broken  down,  are  known  in  the  canyons  of  Colorado,  New  Mexico, 
and  Arizona,  but  they  are  no  longer  occupied  by  the  Indians  who 
formerly  (before  the  coming  of  the  white  men)  lived  in  them.] 

9.  1.93  shows  part  of  still  another  plateau  and  canyon  ;  compare 
it  witli  8  2  as  to  general  altitude  of  the  plateau  ;  depth  of  the  can- 
yon ;  number  of  cliffs  and  slopes  ;  width  of  canyon  at  plateau  level ; 
amount  of  plateau  uplift.    2.  In  which  example,  7  1,  82,  or  93,  do 
you  think  a  longer  time  has  passed  since  uplift  aud  erosion  began  ? 
How  can  you  tell  ?     3.  Complete  in  9  3  the  profile  and  section  on 
the  W.  side  of  the  canyon.    How  far  has  cliff  J  retreated  westward 
since  it  was  first  cut  through  by  the  river?    4.  Which  cliff  has  re- 
treated the  most,  /  or  G  ?    G  or  E  ?    Why?    5.  Is  the  retreat  of 
cliff  E  more  affected  by  the  retreat  of  slope  F  or  of  slope  D  ?    Why  ? 
6.  Above  which  cliffs  is  there  a  nearly  level  bench  or  platform  (from 
top  of  cliff  to  base  of  next  higher  slope)  ?    [7.  Explain  the  origin  of 
the  platform  over  cliff  E ;  over  cliff  G.     (DE,  163.9 ;  DP,  143.9.) 
8.  Why  is  one  of  these  platforms  broader  than  the  other  ?    9.  Why 
is  there  no  platform  over  cliff  C  ?    10.  What  becomes  of  the  talus 
on  slope  B  ?  on  slope  D  ?  on  slope  F?  on  slope  H?    (DP,  144.1.) 

11.  Draw  another  W.  wall  profile,  as  if  the  river  had  worn  down 
its  channel    100'  deeper  and  the  main   cliff   had  retreated  500'. 

12.  About  how  much  additional  retreat  of  the  top  cliff  is  thus 
shown  ?    13.  What  change  in  the  width  of  the  platform  on  E  is 
thus  shown  ? 

10.  [1.  The  canyon  of  the  Colorado  river  has  been  eroded  in  a 
plateau ;    part  of  it  is    mapped  in  36 1.    Locate   on   Plate  40.    A 
cliff  is   shown  where  two  or  more  contours   are  close  together ; 
a  platform,  by  wide-spaced  contours.    What  is  the  altitude  of  the 
plateau  ?   of  the   river  ?    the  depth  of   the   canyon  ?    How  far  is 
the  plateau  rim  S.  of  the  river  ?    2.  How  many  cliffs,  slopes,  and 
platforms  are  shown  ?    3.  Which  cliff,  counting  down  from  the  top, 
seems  to  be  highest  ?    (See  Powell's  Explorations  of  the  Colorado 


36  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

River  of  the  West,  Washington,  1875 ;  a  remarkable  narrative  of 
an  adventurous  journey  down  the  river  in  boats  (see  especially 
p.  100);  many  plates.  Button's  Tertiary  History  of  the  Grand 
Canyon  District.  U.  S.  G.  S.,  Monogr.  II  (see  the  excellent  plates  in 
atlas  of  this  report,  especially  VI);  an  abridgment  of  Button's 
work  is  given  in  the  Second  Annual  Report  of  the  U.  S.  G.  S.  The 
large  contour  map,  Bright  Angel  quadrangle,  Arizona,  by  F.  E. 
Matthes  (from  which  the  map  36  1  is  taken),  is  an  extraordinary 
example  of  topographic  surveying.)] 

11.  1.  If  you  walked  along  the  edge  or  "  rim  "  of  the  plateau,  9  3, 
would  your  path  be  straight  or  irregular  ?  more  or  less  irregular 
than  the  course  of  the  river?  Why?  2.  Why  is  the  edge  of  the 
plateau  in  8  2  more  irregular  than  that  in  7  1  ?  in  9  3  more  irregu- 
lar than  in  8  2  ?  3.  Why  is  the  edge  of  the  uppermost  cliff  /,  9  3, 
more  irregular  than  that  of  the  second  cliff  G,  and  so  on  down  to 
cliff  C  ?  4.  Draw  a  line  (so  far  as  there  is  room)  on  the  front  face 
of  9  3,  beginning  at  the  river,  to  represent  the  profile  of  the  E.  side- 
stream.  5.  How  does  this  differ  from  the  corresponding  profile 
drawn  in  8  2,  as  to  average  slope  ?  as  to  number  of  falls  ?  [6.  In 
9  3  b  the  formations  with  odd  numbers  are  resistant  cliff  makers. 
Draw  profiles  of  canyon  walls  corresponding  to  the  several  posi- 
tions of  the  river,  A,B,  C,D  (as  if  the  profiles  were  in  succession 
farther  and  farther  downstream).]  [7.  Where  in  9  3  is  some  of  the 
coarser  waste  from  the  side  canyons  deposited  ?  (See  9  3  a,  drawn  on 
a  larger  scale.)  8.  What  is  the  form  of  these  deposits  ?  What  name 
is  given  to  them  ?  (DE,  197.4;  DP,  275.9;  G,  38.4  ;  T,  66.5.)  Why 
are  they  not  seen  in  7 1  ?  NOTE  :  When  unusually  heavy  rains 
occur,  a  violent  flood  may  rush  down  a  side  canyon  and  sweep  great 
bowlders  into  the  river ;  before  another  flood  occurs,  the  river  may 
gradually  roll  most  of  the  bowlders  downstream.  9.  What  effect 
has  a  "  fan  "  on  the  width  of  the  river  at  the  fan  front  ?  next  up- 
stream from  the  fan  ?  on  the  slope  of  the  river  ?  on  the  river  cur- 
rent ?  on  the  river  bank  opposite  the  fan  ?  on  the  passage  of  boats 
or  rafts  down  the  river  ?]  [10.  Imagine  that  several  rivers,  like  the 


PLATEAUS   AXD  CANYONS  37 

one  shown  in  9  3,  crossed  the  plateau,  20  to  50  mi.  apart ;  describe 
the  general  appearance  of  the  region.  11.  Would  most  of  the  region 
be  occupied  by  undissected  plateau  surface  or  by  canyons  ?  12.  When 
the  cycle  of  erosion  is  complete,  the  plateaus  would  be  worn  down 
to  a  lowland.  Does  9  3  represent  an  early  or  a  late  stage  of  a  com- 
plete cycle  ?  13.  May  the  plateau  in  9  3  be  described  as  young, 
mature,  or  old?  14.  Compare  the  depth  to  which  the  river  has 
eroded  its  canyon  in  the  plateau  with  the  depth  to  be  eroded  in 
future.  15.  Has  the  river  in  this  part  of  its  course  developed  a 
rather  evenly  graded  course,  or  is  it  still  interrupted  by  steep 
waterfalls  ?  NOTE  :  A  river  with  many  waterfalls  in  a  narrow 
valley  might  be  called  young ;  with  an  evenly  graded  course  but 
without  a  flood  plain,  early  mature ;  with  an  evenly  graded  course 
and  an  open  flood  plain,  late  mature.  16.  In  which  of  these  stages 
is  the  river  in  9  3  ?] 

12.  1.  10  4  is  intended  to  represent  a  later  stage  (many  thousand 
years  later)  in  the  erosion  of  the  plateau  which  is  shown  in  9  3. 
Complete  the  W.  front  section  in  10  4  and  add  letters  corresponding 
to  those  of  9  3.  2.  Compare  9  3  and  10  4  as  to  altitude  of  plateau 
(the  plateau  surface  in  10  4  is  seen  only  in  the  far  right-hand  (NE.) 
corner.  Why  ?)  ;  amount  of  uplift ;  depth  of  canyon ;  altitude  of 
river  in  foreground.  3.  Compare  the  two  figures  as  to  amount  of 
load  received  by  river  from  canyon  walls  (the  steeper  the  walls,  the 
more  waste  falls  from  them)  ;  from  side  canyons  (the  longer  the  side 
canyons,  the  more  waste  they  supply)  ;  fall  of  river  in  feet  per 
mile  (length  of  river  here  shown  in  each  figure,  2  mi.)  ;  width  of 
canyon  bottom  or  floor  (from  talus  to  talus)  ;  width  of  canyon  at 
level  of  plateau.  (In  10  4  the  width  is  (about)  twice  the  distance 
from  background  vertical  scale  to  back  profile  of  cliff  /  in  NE.  corner. 
"Why  ?).  4.  Compare  the  two  figures  as  to  length  of  side  canyons  ; 
number  of  cliffs  and  slopes  shown  E.  of  river.  Why  are  fewer 
cliffs  seen  in  10  4  on  W.  than  on  E.  ?  5.  Compare  the  two  figures  as 
to  breadth  of  platforms;  average  slope  of  canyon  walls  (in  io4, 
slant  of  straight  line  drawn  at  back  of  block  from  top  of  cliff  J 


38  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

to  base  of  lowest  talus).  6.  Where  these  comparisons  show  differ- 
ences, explain  them.  7.  In  the  change  from  9  3  to  10  4,  why  has  the 
widening  of  the  canyon  at  the  top  been  greater  than  the  deepening 
at  the  bottom  ?  [8.  Is  the  retreat  of  cliff  E  more  affected  by  the 
weathering  of  slope  D  or  of  slope  F?  Why?  9.  Which  cliff  face 
tends  to  retreat  more  rapidly,  C  or  E  ?  Why  ?  10.  Why  is  cliff 
face  C  less  distinct  than  E  ?  less  distinct  than  C  in  9  3  ?  11.  Ex- 
plain the  origin  of  the  flat  canyon  floor  in  10  4.  How  does  it  differ 
in  origin  from  the  platforms  ?] 

13.  1.  If  the  plateau  of  io4  were  seen  in  a  still  later  stage  of 
erosion,  what  change  would  you  expect  to  find  in  the  altitude  of 
the  river  ?  in  its  fall  per  mile  ?  in  the  depth  of  the  canyon  ?  in 
the  width  of  the  canyon  floor  ?  of  the  canyon  top  ?  2.  What 
change  would  you  expect  in  the  length  of  the  side  canyons  ?  in  the 
breadth  of  the  platforms  ?  in  the  number  of  cliffs,  slopes,  and  plat- 
forms ?  in  the  irregularity  of  the  plateau  rim  ?  3.  As  the  plateau  is 
more  and  more  eroded,  will  the  term  canyon  be  more  appropriate 
or  less  appropriate  as  a  name  for  its  valleys  ?  4.  Estimate  (roughly, 
in  miles)  the  whole  length  of  the  E.  side  canyon  of  10  4.  5.  Imagine 
other  rivers  and  canyons  like  those  of  104,  20  to  50  mi.  apart. 
Would  traveling  be  easy  or  difficult  along  a  line  about  midway 
between  two  such  rivers  ?  Why  ?  6.  Imagine  that  the  side  canyons 
have  increased  to  lengths  of  from  12  to  30  mi.  What  effect  would 
be  produced  on  the  plateau  where  the  heads  of  two  side  canyons 
meet  ?  7.  Describe  a  route  of  travel  under  such  conditions  about 
midway  between  two  rivers  ?  NOTE  :  When  wide  belts  of  undis- 
sected  plateau  surface  remain  between  the  river  canyons,  the 
plateau  may  be  called  young ;  if  the  main  canyons  are  very  nar- 
row and  the  side  canyons  are  very  short,  the  plateau  is  very 
young ;  as  the  main  canyons  widen  and  the  side  canyons  lengthen, 
so  that  the  belts  of  plateau  surface  are  narrowed  (but  still  retain 
an  even  surface  along  the  divides  between  the  rivers),  the  dissec- 
tion of  the  plateau  may  be  called  early  mature;  when  the  side 
canyons  of  neighboring  rivers  meet  at  their  heads,  the  plateau 


PLATEAUS  AND  CANYOXS  39 

reaches  a  late  mature  stage  of  dissection.  8.  In  what  stage  is  the 
plateau  of  question  5,  above  ?  of  question  6  ?  of  8  2  ?  of  7  1  ?  In 
what  stage  of  development  is  the  river  of  io4?  (See  Note,  end  of 
§  11.)  Explain.  9.  What  are  the  characteristic  features  of  a 
young  plateau  ?  of  a  late  mature  plateau  ?  of  a  very  young  plateau  ? 
of  an  early  mature  plateau?  [10.  10 4 b  represents  cliff  and  talus 
slopes  of  another  plateau  in  greater  detail  than  10  4.  Draw  lines  to 
the  left  of  the  profile  (in  the  air)  to  represent  the  internal  struc- 
ture that  is  indicated  by  the  external  form  ;  shade  lightly  the  harder 
formations.  11.  Where  do  some  strata  of  intermediate  resistance 
occur  (neither  good  cliff  makers  nor  good  slope  makers)  ?] 

14.  [1.  7  5  is  an  outline  map  of  part  of  a  river  system  in  a  dis- 
sected plateau.  How  does  the  scale  of  this  map  compare  with  the 
scale  of  7  1  and  10  4  ?  2.  Let  there  be  only  one  cliff-making  forma- 
tion in  the  structure  of  this  plateau,  and  let  the  line  aa,  1 5, 
represent  the  edge  of  the  cliff  E.  of  the  river  in  an  early  stage  of 
dissection.  (Neglect  the  lines  bb,  cc,  for  the  present.)  3.  Why 
does  the  cliff  line  turn  into  the  plateau  (away  from  the  main  river) 
in  several  sharp  angles  or  reentrants  ?  turn  toward  the  river  in 
several  curves  ?  4.  What  is  the  relation  of  the  reentrants  and  curves 
to  the  side  streams  ?  5.  Why  do  the  reentrants  extend  to  different 
distances  from  the  main  river?  6.  Draw  a  similar  line  a'a'  (be- 
ginning at  N.  end),  to  show  the  corresponding  cliff  W.  of  the  river. 
7.  The  line  bb  may  now  be  taken  to  show  the  same  cliff  at  a  later 
stage  of  erosion.  Is  the  cliff  now  less  or  more  irregular  than  before  ? 
Why  ?  8.  Draw  a  corresponding  line  b'b'  W.  of  the  river.  The 
side  ravines  are  now  long  enough  to  be  called  side  canyons.  The 
line  cc  shows  a  still  later  position  of  the  same  cliff :  what  peculiar 
feature  does  it  show  at  R?  9.  How  has  this  part  of  the  plateau 
surface  come  to  be  separated  from  (or  to  "  lie  out "  from)  the  rest  of 
the  plateau  ?  Such  an  isolated  part  is  called  an  outlier.  10.  Draw 
a  third  cliff  line  W.  of  the  river,  corresponding  to  cc.  How  many 
outliers  does  it  show  ?  Explain  their  origin.  11.  WTill  these  out- 
liers increase  or  decrease  in  size  as  erosion  continues  ?  Why  ? 


40  EXERCISES  IX  PHYSICAL  GEOGRAPHY 

12.   Are  outliers  likely  to  increase   or  to  decrease  in  number  as 
erosion  progresses  ?  Why  ?] 

15.  XOTE  :  If  §  14  is  omitted,  omit  §  15  also.     [1.  Another  use 
may  now  be  made  of  7  5  :  it  may  be  taken  to    represent  a   well- 
dissected  plateau,  with  three   cliff  makers,   a,  b,  c,  separated  by 
slope  makers.    2.  Which  cliff  maker  stands  highest  in  the  plateau 
structure  ?    How  can  you  tell  ?    3.  A  section  along  the  line  A/TV, 
7  5,  is  given  in  7  6.    Complete,  in  7  7,  a  section  along  the  line  QS, 
7  5.     (Measure  distances  in   7  5  on  a   strip  of   paper,  from   Q  to 
cliffs    and   streams,    and    transfer    the    distances    to    7  7.)     4.  A 
hachured  map  of  a  similar  plateau  is  shown  in  7  9.     How  are  the 
steep  cliff  faces   indicated  ?   the  talus   slopes  ?    the  nearly  level 
plateau  surface  and   the  narrow  platform  over  the  middle  cliff? 
5.  Draw  hachures  for  the  rest  of  the  figure.    6.  7  8  is  a  contour 
map  of  part  of  a  similar  dissected  plateau.    Why  are  the  contours 
so  crowded  on  the  cliff  faces  ?     What  is  the  contour  interval  ? 
7.  What  is  the  altitude  of  the  plateau  surface  ?    About  how  deep 
is  the  main  canyon  ?    8.  Draw  contours  for  the  rest  of  7  8.    9.  From 
which  figure  can  you  gain  the  best  idea  of  the  plateau  forms, — 
the  outline  map  (7  5),  the  profiles  (7  6  and  7  7),  the  hachured  map 
(7  9),  or  the  contoured  map  (7  8)  ?  Why  ?  10.  From  which  map,  7  5, 
7  8,  or  7  9,  can  an  accurate  cross  section  be  best  drawn  ?    Why  ? 
11.  Which  kind  of  a  map  would  you  prefer  in  finding  your  way 
across  a  dissected  plateau  ?    Why  ?] 

16.  [1.    Consider   a  broad   plateau   hundreds  of   miles    across. 
What  general  effect  will  the  branching  rivers  and  [frequently  in- 
sequent]  side  streams  of  a  large  river  system  (or  of  several  river 
systems)  have,  as  time  passes,  on  the  form  of  such  a  plateau  ? 
2.  The  line  cccc,  8  10,  shows  a  profile  across  part  of  such  a  plateau. 
How  many  cliff-making  formations   are  represented  ?     How   far 
apart  are  the  two  rivers  r,  r'  ?    3.  With  which  one  of  the  plateaus, 
7  1  to  10  4,  does  the  profile  cc,  8  10,  most  nearly  correspond  as  to 
stage  of  erosion  ?    4.  Draw  profiles  (beginning  at  the  right)  for 
two  earlier  stages,  b  and  a,  in  8  10 ;  for  two  later  stages,  d  and  e. 


PLATEAUS  AND  CANYONS  41 

5.  When  the  profile  has  reached  the  stage  d,  which  part  of  it 
represents  a  mesa  ?  in  stage  e,  which  part  represents  a  butte  ? 
(DE,  171.3;  DP,  150.6;  G,  91.9 -;  T,  82.8.)  6.  What  features 
occupy  the  greatest  area  in  stage  e  ?  What  features  are  most 
conspicuous  in  the  landscape  of  stage  e  ?  1.  Draw  profiles  for  still 
later  stages, /and  g.  8.  What  has  become  of  the  butte  (stage  e)  in 
stage  f?  9.  To  what  form  has  the  lower  cliff  maker  been  reduced 
in  stage  f?  in  stage  g  ?  10.  What  feature  occupies  the  greatest 
area  in  stage  g  ?  What  is  then  the  most  conspicuous  feature  ? 
11.  Draw  a  profile  for  stage  h.  What  name  might  be  given  to  the 
region  in  this  stage  ?  12.  Describe  the  general  appearance  of  the 
district  in  stage  «;  in  stage  e  ;  in  stage  g ;  in  stage  A-.] 

17.  NOTE  :  If  §  1G  is  omitted,  omit  §  17  also.     [1.  In  which  of 
the  various    stages,  a  to  h,  8  10,  might  the  district  there  repre- 
sented in  profile  be  called  a  young  plateau  ?  an  old  lowland  ?  a 
maturely  dissected  plateau  ?    2.  Explain  the  altitude  of  the  low- 
land or  peneplain  r'/ir  in  relation  to  baselevel  ?    3.  In  which  stage 
(young,  mature,  or  old)  of  erosion  of  the  plateau  would  its  val- 
leys be  called  canyons  ?    would  roads  and  settlements  be  found 
chiefly  on  the  highlands  ?    on  the  lowlands  ?    4.  In  which,  stage 
would  outliers  be  common  ?  would  the  lower  cliff  maker  be  reduced 
to  isolated  buttes  ?    5.  AVhere  would  such  buttes  stand  in  relation 
to  the  main  rivers  ?     6.  How  is  the  term  cycle  of  erosion  illus- 
trated by  8 10  ?     7.  Suppose  that  when  stage  g  had  been  reached, 
a  general  uplift  of  the  region  occurred ;  draw  a  [red]  line  in  8  10 
to  show  the  profile  of  the  district  when  the  stage  of  youth  had  been 
reached  in  the  new  cycle  of  erosion  (introduced  by  the  new  uplift) ; 
when  the  stage  of  maturity  had  been  reached  in  the  cycle.] 

18.  [1.  36  2  represents  a  plateau  dissected  by  canyons.    Locate  it 
on  Plate  40.    In  what  part  of  what  state  is  it  ?    2.  State  the  scale  ; 
the  contour  interval  ;  the  general  altitude  of  the  plateau  ;  the  depth 
and  breadth  of  the  main  canyons  ;  the  length  of  the  side  canyons. 
3.  Is  the  cycle  of  erosion  half  accomplished,  nearly  completed,  or 
only  well  begun  ?    4.  In  what  stage  of  dissection  is  the  plateau  ? 


42  EXERCISES   IN  PHYSICAL  GEOGRAPHY 

5.  36  3  is  another  part  of  the  same  plateau,  about  50  mi.  NE.  of 
36  2  ;  the  same  river  is  shown  in  both  figures.  6.  In  what  part  of 
36  3  is  part  of  the  undissected  plateau  surface  seen  ?  What  is  its 
altitude  ?  [7.  Can  you  explain  why  Purgatoire  river  flows  NE.  ? 
To  what  class  does  it  seem  to  belong  ?]  8.  Print  on  36  3  PLATEAU, 
CLIFF,  PLATFORM,  SIDE  CANYON,  VALLEY  FLOOR,  in  their 
proper  places.  9.  How  many  cliff-making  formations  are  here  ex- 
posed ?  How  wide  is  the  platform  between  the  two  cliffs  ?  How 
high  is  each  cliff  ?  How  long  (about)  are  the  side  canyons  ?  How 
wide  is  the  valley  floor  ?  10.  In  what  stage  of  dissection  is  the 
plateau?  11.  Compare  the  canyon  of  Purgatoire  river  in  36  2  and 
36  3  (in  each  case  measure  canyon  width  from  plateau  rim). 
12.  What  general  rule  of  canyon  form  is  here  illustrated?  (See 
question  4,  §  6.)  13.  Locate  the  district  shown  in  364  on  Plate  40. 
In  what  part  of  the  Allegheny  plateau  does  it  occur  ?  (See  DE, 
Fig.  78  ;  DP,  Fig.  92.)  State  'the  scale  and  contour  interval. 
14.  What  is  the  altitude  of  the  plateau  ?  of  the  valley  floors  ?  the 
relief  of  the  district  ?  15.  What  is  the  width  of  the  upland  belt 
(between  the  side-valley  heads)  E.  of  Battle  Creek  valley  ?  How 
long  and  wide  are  the  upland  spurs  (to  W.)?  Which  occupy  the 
greater  area,  the  plateau  surfaces  or  the  valleys  (from  rim  to  rim 
of  plateaus)  ?  16.  In  what  stage  of  dissection  is  the  plateau  in 
this  district  ?  (See  Note  following  question  7,  §  13.)  17.  In  what 
stage  of  development  are  the  main  streams  ?  18.  Where  do  water- 
falls occur  ?  In  what  stage  of  development  are  the  upper  parts  of 
the  side  streams  ?  19.  Locate  the  district  shown  in  36  5,  on  Plate  40. 
What  is  the  scale  ?  the  contour  interval  ?  20.  What  is  the  altitude 
of  the  valley  floor  (or  flood  plain)  of  Blackford  creek  ?  the  altitude 
of  the  hilltops  ?  the  relief  of  the  district  ?  21.  Which  occupy  the 
greater  area,  the  hilltops  or  the  valley  floors  ?  22.  This  region 
was  once  an  even  upland  (or  plateau  of  moderate  altitude).  In  what 
stage  of  dissection  is  it  now  ?  23.  In  what  stage  of  development 
is  Blackford  creek  ?  24  If  this  creek  is  here  700'  above  sea  level, 
why  does  it  not  wear  its  valley  floor  down  lower?  25.  To  what 


PLATEAUS   AXD   CANYONS  43 

class  do  the  side  streams  in  36  2-5  apparently  belong  ?    (See  Exer- 
cise III,  §  10,  question  20.)    Why  ? 

19.  [1.  Locate  9  3  c  and  9  3  d  on  Plate  40.  In  what  part  of  the  Alle- 
gheny plateau  are  they  ?  (See  DE,  Fig.  78  ;  DP,  Fig.  92.)  2.  What  is 
the  scale  of  these  maps  ?  the  contour  interval  ?  3.  What  river  is 
shown  in  9  3c  ?  How  deep  is  its  valley  beneath  the  neighboring  up- 
lands ?  4.  How  wide  is  the  river  ?  the  valley  floor  ?  5.  Draw  a  [red] 
line  around  the  strip  of  valley  floor  NW.  of  the  river,  and  around 
the  strips  of  valley  floor  SE.  of  the  river  (neglect  the  valley  floor 
of  the  branch  stream  on  NE.)  ;  a  [blue]  line  where  the  river  touches 
the  base  of  the  steep  valley  side.  6.  As  you  follow  down  the  river, 
how  are  the  successive  valley-floor  strips  arranged  ?  7.  Compare  the 
course  of  Purgatoire  river,  36  2,  with  the  course  of  the  Ohio  river, 
93c,  and  of  Captina  creek,  93cZ.  Which  of  these  streams  might  be 
described  as  nearly  straight  ?  moderately  curved  (or  sinuous)  ? 
strongly  curved  (or  serpentine,  or  meandering}  ?  8.  Which  of 
these  streams  has  eroded  a  meandering  valley  ?  (DE,  271.7-  ;  DP, 
253.4  ;  G,  51.8  ;  T,  Fig.  143.)  9.  As  a  meandering  valley  is  widened, 
is  the  valley  floor  normally  on  the  inside  or  outside  of  the  stream 
curves  ?  On  which  side  of  the  stream  curve  is  the  steeper  valley 
side  ?  (DE,  258.9.)  10.  Shade  [blue]  the  normal  valley  floors  and 
[red]  the  normal  steep  valley  sides  of  93d.  11.  Do  any  abnormal 
cases  occur  ?  If  the  stream  there  followed  the  broken-line  curve, 
would  these  cases  be  normal  or  abnormal  ?  12.  What  change  of 
stream  course  has  probably  taken  place  there  ?  13.  Which  meander 
curve  is  entered  by  a  spur  with  a  low,  narrow  neck  ?  14.  Locate 
10  4  c  on  Plate 40.  Of  what  plateau  is  it  a  part?  15.  What  is  the 
altitude  of  the  plateau  in  io4c?  the  depth  and  breadth  of  Cheat 
river  canyon  ?  16.  In  what  stage  of  development  are  the  river  and 
its  canyon?  17.  Are  the  side  canyons  long  or  short?  Are  their 
streams  of  strong  or  gentle  fall  ?  18.  Locate  10  4d  on  Plate  40.  In 
what  state  is  it  ?  What  is  the  altitude  of  the  highest  and  lowest 
parts  ?  19.  Begin  near  the  NW.  corner  and  draw  a  [red]  line  east- 
ward along  the  divide  between  the  NE.  and  the  SE.  streams.  NOTE  : 


44  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

The  streams  are  drawn  in  broken  lines  to  indicate  that  they  cease 
flowing  in  dry  weather.  20.  Does  the  divide  follow  a  uniform  alti- 
tude ?  21.  All  this  district  was  once  a  plateau  of  at  least  5000' 
altitude.  To  which  profile  in  8  10  does  it  now  correspond  ?  What 
stage  of  dissection  has  it  now  reached  ?  22.  How  many  buttes  are 
shown?  Explain  their  origin.  23.  To  what  features  in  10 4d  does 
10  4  a  correspond  ?  24.  What  is  the  origin  of  the  plain  in  io4a  ?  To 
which  profile  in  8  10  does  it  correspond  ?  25.  In  what  stage  of  the 
cycle  of  erosion  is  the  district  of  the  Enchanted  Mesa?  (DE,  172.3  ; 
DP,  151.5.)  26.  In  what  part  of  the  United  States  is  it  ?  27.  Locate 
(roughly)  on  Plate  40  the  canyon  of  Kanawha  river,  shown  in  the 
figure  at  the  bottom  of  this  page.  Compare  this  canyon  with  the 
canyon  of  Cheat  river,  io4c.  28.  In  what  stage  of  development  is 
the  Kanawha  canyon  ? 

20.  Define  :  Preliminary  §,  canyon  ;  §  1,  cliff,  outcrop,  structure  ; 
§  2,  formation,  cliff-making  formation,  slope-making  formation  ;  §  3, 
retreat  or  recession  of  waterfalls ;  §  4,  retreat  or  recession  of  cliffs, 
talus  ;  [§  8,  profiles  and  sections;]  §  9,  platform;  [§  11,  alluvial 
fan,  young  river,  early  mature  river,  late  mature  river  ;  §  13,  young 
plateau,  maturely  dissected  plateau  ;  §  14,  outlier  ;  §  1(5,  mesa,  butte  ;] 
§  17,  cycle  of  erosion ;  [§  19,  meandering  river,  meandering  valley]. 


EXERCISE  V.    THE   SCULPTURE  OF  MOUNTAINS 

OBJECT.    To  explain  various  features  of  mountain  ranges. 

Preliminary.  11 1  gives  a  general  view  over  a  rolling  district  of 
low  hills  and  shallow  valleys,  all  covered  with  a  deep  weathered 
soil.  The  district  is  drained  by  a  large  river  and  many  smaller 
streams,  all  flowing  quietly  and  smoothly  through  their  flood  plains. 
The  soils  vary  from  place  to  place,  as  if  the  underlying  rocks  were 
of  different  kinds.  Some  low  mountains  rise  in  the  E.  and  NW. ; 
there  the  soil  is  thinner  and  more  stony.  The  view  is  cut  off  in 
front  by  a  vertical  section,  the  baseline  of  which  is  at  sea  level. 
Altitudes  are  marked  at  various  points  ;  a  scale  of  altitudes  is 
drawn  near  the  NE.  corner,  and  a  scale  of  miles  along  the  front 
baseline.  This  exercise  uses  11, 12, 14, 1:3, 1C,  1-22  [also  37  1-5].  Note 
that  Plate  14  is  to  be  used  before  Plate  13. 

1.  1.  The  distance  along  the  winding  river  A  to  E,  11 1,  being 
30  mi.,  what  is  the  average  fall  of  the  river  in  feet  per  mile  ?  2.  If 
E  is  600  mi.  from  the  river  mouth,  what  is  the  average  fall  from  E 
to  the  sea  ?  3.  What  is  (about)  the  width  of  the  main  river  flood 
plain  ?  4.  The  altitudes  on  stream  (or  small  river)  F  (SE.  corner  of 
11 1)  are  indicated  for  points  two  miles  apart.  What  is  its  average 
fall  ?  the  width  of  its  flood  plain  ?  5.  Why  may  the  streams  of  this 
district  be  described  as  "  thoroughly  graded  with  respect  to  their 
general  baselevel "  (the  ocean)  ?  6.  What  is  the  general  altitude  of 
the  interf  uves,  or  spaces  between  the  small  rivers  (see  foreground 
profile)  ?  their  relief  ?  7.  What  is  the  altitude  of  the  highest  moun- 
tain on  the  N.  border  ?  the  general  relief  in  that  mountain  group  ? 
NOTE  :  To  find  (roughly)  the  height  of  the  mountain  above  the  sur- 
rounding district,  draw  a  straight  line  between  the  parts  of  the  N. 
border  marked  900',  and  measure  the  mountain  height  above  this  line. 

45 


46  EXERCISES   IX   PHYSICAL   GEOGRAPHY 

2.  1.  If  you  should  walk  eastward  from   IF  to  W',  how  many 
times  would  you  go  uphill  and  downhill  ?    about  how  many  feet 
would  you  ascend  and  descend  in  each  case  ?    2.  Print  D  at  points 
where  you  cross  divides  between  the  small  rivers  /,  H,  G,  F;  print 
d  where  you  cross   subdivides   between  side  streams.    3.  Draw  a 
line  up  and  down  hill,  eastward  from  X  to  A'',  and  answer  the  same 
questions  as  in  question  1.    4.  Draw  an  E.-W.  line  through  Y  (W. 
center  of  figure)  and  print  D  where  the  line  crosses  the  divide  be- 
tween the  two  streams  there  shown.    5.  Draw  similar  lines  through 
Z,  Z,  Z,  an.d  mark  the  divides  on  them.    6.  Draw  a  broken  [red] 
line  southward  from  Q,  on  the  1ST.  border,  through  Y  to  the  S.  border 
of  the  figure,  dividing  the  drainage  area  of  the  main  river  from 
that  of  the  W.-flowing  rivers.    7.  Draw  a  broken  [red]  line  west- 
ward from  M,  on  the  E.  border,  to  M'  near  main  river,  dividing  the 
drainage  area  of  the  main  river  AE  from  that  of  the  small  rivers 
F,  G,  H,  J.    8.  Should  the  various  divides  and  subdivides  that  you 
have  marked  be  described  as  "  high,  sharp,  and  well  denned  "  or  as 
"  low,  gently  rounded,  and  ill  denned  "  ? 

3.  1.  Draw  a  line  along  stream  F  and  its  NW.  branch,  over  the 
divide  at  its  head,  and  down  stream   R  ;   mark   D  at  the  divide. 
NOTE  :   In  16  15  the  small  crosses  (  x   X  )  represent  the  altitudes 
of  the  two-mile  points  on  streams  F  and  R  of  11 1  ;  and  the  dots 
in  the  small  circles  represent  the  altitudes  of  the  low  hills  on  the 
neighboring  interfluves.    (The  vertical  scale  in  16  15  is  the  same  as 
in  11 1  ;  the  horizontal  scale  is  smaller.)    2.  Draw  a  line  through 
the  crosses  ;   through  the  dots.    What  do  these  lines  represent  ? 
Print  F  and  R  near  these  lines  ;  draw  a  short  vertical  line  at  the 
divide  between  streams  .F  and  R.     [3.  Suppose  the  district  of  11  1 
to  be  inhabited  in  this  stage  of  its  history  ;  locate  a  city  and  some 
villages  in  the  SE.,  central,  and  NW.  parts  of  the  district ;  connect 
some   of  them  by   a  railroad  (heavy  line)  and  by  several   roads 
(light  lines).    NOTE  :  The  railroad  should  not  have  grades  of  more 
than  100'  in  a  mile  ;  the  roads  seldom  more  than  500'  in  a  mile. 
4.  What  are  the  chief  difficulties  that  would  be  met  in  making  the 


THE  SCULPTURE  OF  MOUNTAINS  47 

roads  and  the  railroad  ?  5.  Which  parts  of  the  district  are  well 
adapted  to  farming?  Which  parts  will  probably  remain  forested 
while  the  rest  is  cultivated?  6.  Which  parts  are  liable  to  over- 
flow by  river  floods  ?  How  much  of  the  main  river  appears  to  be 
navigable  for  river  boats  ?] 

4.  1.  12  2  shows  another  stage  in  the  history  of  the  same  dis- 
trict, uncounted  thousands  of  years  later  than  the  stage  shown  in 
11 1.  2.  Look  at  the  middle  W.  part  of  12  2.  Follow  the  broken 
line  O  O'O"  from  W.  to  E.  and  note  the  altitudes  along  it ;  note  that 
this  part  of  the  district  may  be  described  as  "arched"  or  "up- 
warped."  3.  Begin  in  the  SE.  corner  of  the  district  and  follow 
the  line  NN',  noting  the  change  of  altitude  along  it.  What  has 
happened  in  this  part  of  the  district  ?  4.  Begin  at  the  middle  of 
the  E.  side,  and  follow  the  line  MM'Q'Q  to  the  N.  border  ;  this  line 
may  be  described  as  "  following  the  crest  of  the  arch,"  or  the  "  crest 
of  the  upwarping."  5.  What  directions  does  the  crest  line  follow  ? 

6.  Is  the  amount  of  upwarping  uniform  all  along  the  crest  line  ? 

7.  Near  the  head  of  which  stream  is  it  least  ?   NOTE  :  The  upwarp- 
ing of  the  surface,  as  here  shown,  is  much  stronger  than  ordinarily 
occurs  in  mountain  ranges.    The  upwarping  is  exaggerated  in  these 
figures,  so  as  to  bring  well-developed  forms  into  a  small  district 
for  easy  study.    The  origin  of  the  forces  which  slowly  warp  the 
earth's  heavy  crust  is  not  well  understood,  but  the  great  strength 
and  long-continued  action  of  the  forces  cannot  be  doubted;  they  do 
not  seem  to  be  related  to  volcanic  action.    8.  In  16  15  the  dots  in 
the  larger  circles  represent  several  points  on  the  line  NN',  122. 
Draw  a  curve  through  the  dots.    What  does  this  curve  represent  ? 
9.  Draw,  beneath  this  curve,  the  profiles  of  streams  F  and  R  (see 
small  crosses  +  +).     Print  F  and  R  near  these  profiles  ;  draw  a 
short  vertical  line  at  the  divide.    10.  How  many  feet  beneath  the 
upland  is  the  deepest  part  of  each  valley  ?    11.  Why  is  stream  F 
shorter,  and  why  is  R  longer  than  in  the  corresponding  profiles 
previously  drawn  in  16  15  ?    [12.  Why  may  F  be  described  as  "be- 
headed by  warping"?  R,  as  "extended  by  warping"?]    13.  What 


48  EXERCISES  IN  PHYSICAL   GEOGRAPHY 

is  now  the  average  fall  of  F  ?  14.  In  so  steep  a  stream  there  will 
be  many  falls  and  rapids  ;  the  water  will  flow  swiftly  in  a  narrow 
channel,  plunging  and  foaming ;  at  times  of  flood  the  rushing  stream 
or  torrent  will  sweep  along  large  bowlders.  In  what  stage  of  devel- 
opment is  such  a  stream  ? 

5.  1.  If  you  went  E.  along  line  WW,  12  2,  how  many  times  would 
you  go  up  and  down  hill  ?    2.  Draw  a  similar  line  XX'.    3.  Stream 
G  has  three  forks, — east,  middle,  and  west;  compare  profiles  WW 
and  XX'  where  they  cross  the  valley  of  the  E.  fork  of  G  ;  the  W. 
fork.    [4.  Draw  in  16  7  the  cross  profile  (1)  of  the  W.  fork  of  G, 
on  line  WW  in  12  2;  (2)  of  the  small  E.  branch  of  H  on  line  XX' ; 
(3)  of  J  on  WW;  (4)  of  F  on  WW' ;  (5)  of  the  three  forks  of  G  on 
A'A";  (6)  of  H  on  VV'.    5.  How  does  cross  profile  (3)  differ  from 
(1)  and  (2)  ;  (4)  and  (5)  from  (3)?  (6)  from  (4)  and  (5)?]   6.  Why 
are  the  valleys  of  F,  G,  H,  etc.,  in  12  2  unlike  the  corresponding 
valleys  in  ill?    7.  Why  may  the  streams  of  12  2  be  described  as 
revived  or  rejuvenated  ?   8.  What  has  caused  their  revival  ?    9.  Why 
may  the  new  valleys  be  described  (in  cross  profile)  as  sharp  ^ -shaped 
valleys  ?    10.  Why  did  not  the  streams  in  11 1  erode  sharp  V-shaped 
valleys  ?    11.  Which  parts  of  the  valleys  in  122  most  nearly  resem- 
ble the  valleys  of  11 1  ?  Why  ?  [12.  Compare  the  steep  valley  sides 
in  122  with  the  neighboring  uplands,  as  to  depth  of  soil  ;  as  to 
amount  of  bare  rock  ledge  exposed.] 

6.  [1.  A  small  part  of  the  Sierra  Nevada  mountains  is  shown 
in  37  1.    Locate  this  district  on  Plate  40.    In  what   part  of  what 
state  is  it  ?   What  is  the  scale  of  the  map  (miles  to  an  inch)  ?  the 
contour  interval  ?    2.  What  is  the  altitude  of  the  upper  valley  of 
Turnback  creek  ?    3.  Is  the  valley  floor  there  narrow  or  broad  ? 
4.  How  much  higher  than  this  valley  floor  are  the  hills  2  mi.  to  the 
W.  ?    5.  How  deep  are  the  valleys  of  Tuolumne  river  and  its  north 
fork?    Are  they  broad  or  narrow  floored?    Are  the  valley  sides 
steep  or  gently  inclined  ?    6.  By  what  sort  of  a  valley  is  the  open 
upland  valley  of  upper  Turnback  creek  connected  with  the  deep 
and  narrow  valley  of  Tuolumne  river  ?    7.  How  many  other  creeks 


THE  SCULPTURE  OF  MOUNTAINS  49 

show  similar  features  ?  8.  Compare  the  uplands,  the  upland  hills 
(or  mountains),  the  deep  main  valleys,  and  the  side  valleys  of  this 
district  in  the  Sierra  Nevada  with  corresponding  features  in  12  2. 
9.  Why  may  Tuolumne  river  be  described  as  "revived"?  10.  Ex- 
plain the  origin  of  the  deep  valleys  of  this  district.  11.  A  small  part 
of  the  Front  range  of  the  Eocky  mountains  is  shown  in  37  2.  Locate 
this  district  on  Plate  40.  In  what  part  of  what  state  is  it?  What 
is  the  scale  (miles  to  an  inch)  ?  the  contour  interval  ?  12.  In  this 
part  of  the  Kocky  mountains  do  the  highest  summits  rise  in  sharp 
peaks  and  ridges,  or  in  a  broad  rolling  highland  ?  13.  What  is  the 
general  altitude  of  the  highland  area  ?  14.  How  deep  are  the  valleys 
below  the  highland?  15.  What  is  the  general  altitude  of  the  val- 
ley floors  ?  16.  Do  you  think  the  valleys  may  be  worn  much  deeper 
in  future  ?  Explain.  17.  What  is  the  probable  origin  of  the  forms 
here  shown  ?] 

7.  1.  In  12  2  which  parts  of  the  main  river  (indicate  by  letters 
A,  B,  etc.)  flow  in  steep,  rock-walled  gorges  or  canyons?  on  plains? 
2.  What  is  the  average  fall  of  the  river  in  the  farther  gorge  (length 
here  shown,  4  mi.)  ?  in  the  nearer  gorge  (length,  11  mi.)  ?  on  the 
farther  plain  (river  length,  11  mi.)  ?  on  the  nearer  plain  (river 
length  here  shown,  4  mi.)  ?  3.  Will  the  river  current  be  faster  or 
slower  in  gorge  CD  than  in  the  corresponding  part  of  ill?  4.  Com- 
pare the  breadth  of  this  part  of  the  river  in  the  two  figures  ;  explain 
the  difference.  5.  In  16  9  a  profile  along  the  main  river  of  11 1  is 
shown  (looking  E.)  by  the  line  A'E' ;  the  main  river  of  12  2,  by  A"E". 
Lay  a  ruler  (or  straight  edge  of  sheet  of  paper)  along  the  part  A  "B", 
and  compare  its  slope  with  that  of  the  other  parts.  6.  How  is  the 
depth  of  the  gorge  CD  indicated  in  16  9  ?  What  is  the  depth  in  feet  ? 
(See  the  vertical  scale  in  16  9.)  7.  What  relation  exists  between 
depth  of  gorge  and  amount  of  upwarping  ?  8.  Where  would  you 
go  in  122  to  get  the  best  view  of  the  deep  rock  structures  that 
underlie  the  upwarped  uplands  ?  NOTE  :  The  complicated  disorder 
of  rock  structure  in  such  districts  as  are  here  considered  is  illus- 
trated in  the  front  corner  sections  of  16  13,  and  (less  distinctly)  in 


50  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

the  shading  of  the  canyon  walls  in  that  figure ;  see  also  the  front 
section  of  16  20. 

8.  1.  Why  may  the  dotted  area  B-C,  12  2,  be  described  as  a  basin 
plain?    2.  Where  have  the  layers  of  gravel  and  sand,  or  alluvial 
deposits,  which  cover  this  plain,  come  from?    3.  The  thickness  of 
these  alluvial  deposits,  determined  by  deep  wells  bored  at  various 
points,  is  shown  by  vertical  lines  beneath  the  river  profile  B"C", 
16  9 ;  draw  a  curve  through  the  lower  end  of  these  vertical  lines. 
4.  What  does  this  curve  represent?    Compare  it  with  the  curve 
C"D"  in  the  same  figure.    5.  Why  may  the  inclosed  district  occupied 
by  the  basin  plain  be  described  as  having  been  bent  down,  or  down- 
warped?    6.  Why  have  layers  of  gravel  and  sand  been  deposited  in 
the  down-warped  area?    What  is  their  greatest  total  thickness? 
[7.  What  mountains  inclose  the  great  plain  of  the  "  valley  of  Cali- 
fornia" on  the  E.  and  W.  ?   (DE,  265.4,  267.2  ;  DP,  288.5,  291.1-  ; 
G,  161.1  ;    T,  68.2.)     8.  The  mountain  valleys   decrease  in  depth 
toward  the  great  plain;  there  the  streams  flow  out  on  nearly  flat 
alluvial  fans,   which    unite   to   form   the  great  alluvial   plain   of 
the    "valley"   (over   300  mi.   long,  about  50  mi.  wide).    9.  Point 
out  similar  features  in  122.     10.  What  is  the  probable  origin  of 
the  "valley  of  California"?    11.  By  what  two  chief  rivers  is  it 
drained?    Through  what   "drowned  valley"  (or  bay)  do  the  river 
waters  reach  the  Pacific  ocean  ?] 

9.  1.  If  the  warping  in  the  region  of  11 1  had  taken  place  very 
rapidly,  and  raised  the  high-crested  barrier  MM'Q'Q,  12  2,  across  the 
main  river  course,  and  the  river  had  been  stopped  for  a  time,  where 
would  a  large  lake  have  been  formed  ?   2.  Where  would  the  rising 
waters  of  such  a  lake  have  found  an  outlet  ?   Why  ?    (The  upwarp- 
ing  of  the  region  NE.  of  the  district  here  shown  is  supposed  to  be 
higher  than  the  line  MM'Q'Q.)    3.  There  is  no  sign  of  a  lake  (except 
the  small  oxbow  lakes,  made  by  the  river)  in  the  basin  plain  ;  and 
the  gorge  CD  has  been  eroded  along  the  course  that  the  river  fol- 
lowed previous  to  (or  antecedent  to)  the  warping.    4.  Then  what 
must  be  concluded  as  to  the  rapidity  of  the  warping  in  this  region  ? 


THE  SCULPTURE   OF  MOUNTAINS  51 

5.  What  must  be  concluded  as  to  the  rate  of  upwarping  of  the  arch 
MM'Q'Q,  12  2,  as  compared  to  the  rate  of  down-cutting  by  the  river 
in  the  gorge  CD  ?  6.  Why  may  the  river  in  the  gorge  CD  be  classed 
as  an  antecedent  river  ?  (DP,  258.2.)  [7.  The  Sacramento  river  has 
its  upper  course  on  the  broad  basin  plains  of  NE.  California.  Locate 
it  on  Plate  40.  8.  Through  what  mountains  does  it  then  flow  west- 
ward ?  What  is  the  origin  of  these  mountains?  (See  §  6,  above.) 

9.  In  these  mountains  the  upper  Sacramento  river  follows  a  deep, 
steep-sided,  narrow  gorge.    To  what  class  does  this  river  belong  ? 

10.  The  river  Meuse  flows  N.  from  the  open  country  of  N.  France, 
through  a  deep,  narrow  gorge  in  the  arched  Ardennes  highlands  to 
the  lowlands  of  Belgium  ;  locate  the  Ardennes  on  Plate  43.   (See  also 
DP,  Fig.  160.)    The  highlands  have  a  gently  rolling  surface  ;  their 
broad  crest  extends  E.-W.  at  an  altitude  of  (about)  300-400  meters. 
The  walls  of  the  Meuse  gorge  and  its  side  gorges  show  greatly 
disordered  rocks.    11.  Point  out  similar  features  in  122.    (NOTE: 
There  is  nothing  in  N.  France  to  correspond  to  the  basin  plain 
BC,  12  2.)    12.  What  do  you  think  is  the  origin  of  the  Ardennes  ? 
13.  To  what  class,  does  the  Meuse  river  probably  belong  ?    14.  Do 
you  think  that  the  uplift  of  the  Sierra  Nevada  and  the  Ardennes 
was  sudden  or  gradual  ?  Why  ?] 

10.  1.  Draw  tn  12  2  a  broken  [red]  line  from  Q'  (W.  of  gorge  CD) 
northward  along  the  divide  between  the  E.-sloping  drainage  area  of 
the  main  river  and  the  W.-sloping  drainage  area  of  several  smaller 
rivers.  2.  Where  is  the  greatest  change  in  this  divide  from  the 
corresponding  divide  in  11 1  ?  3.  Why  may  stream  K',  12  2,  be  de- 
scribed as  having  been  beheaded  by  warping  ?  stream  K,  12  2,  as 
diverted  by  warping  ?  4.  Why  has  part  of  stream  K  been  diverted 
by  warping,  while  the  main  river  A  E  has  held  its  antecedent  course 
in  spite  of  the  warping  ?  5.  What  sort  of  rivers  (as  to  size)  would 
most  likely  preserve  their  antecedent  courses  in  a  slowly  warping 
region  ?  6.  Draw  broken  and  dotted  [red]  lines  to  mark  some  of 
the  divides  and  subdivides  of  the  small  rivers  F,  G,  H,  in  12  2. 
7.  Are  the  divides  and  subdivides  sharp  and  definite,  or  broadly 


52  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

rounded  and  indefinite  ?    [8.  Draw  similar  [red]  divides  and  sub- 
divides in  37  1  and  37  2.    Are  the  divides  sharp  or  rounded  ?] 

11.  1.  What  is  the  form  of  the  waste  (alluvial)  deposits  laid 
down  in  12  2  by  the  rivers  and  streams  at  the  base  of  the  upwarped 
S.  and  W.  slopes  ?  (DE,  265.2  ;  DP,  288.3  ;  G,  42.8  ;  T,  66.5.) 
2.  How  many  such  forms  can  you  count  in  12  2  ?  3.  Were  these 
deposits  made  because  of  down-warping  of  the  foreground  (com- 
pare front  borders  of  11 1  and  12  2),  or  because  of  increase  in  the 
load  of  the  streams  ?  4.  Which  of  these  fans  may  be  described  as 
independent  ?  which  as  laterally  confluent  ?  [5.  Draw  a  [red]  line 
to  represent  a  road  running  E.-W.  about  a  mile  N.  of  the  front 
border  of  12  2 .  Would  it  ascend  or  descend  as  it  approaches  the 
rivers  F,  G,  If,  J,  DE  ?  Explain.  6.  Draw  [blue]  lines  to  represent 
each  of  these  rivers  in  a  new  course  on  its  fan.  What  difficulties 
would  these  river  changes  impose  on  road  construction  ?  7.  Draw 
a  similar  E.-W.  road  in  11  1.  How  does  its  relation  to  the  streams 
differ  from  that  of  the  road  in  12  2  ?]  [8.  Why  may  the  surface  of 
a  fan  be  described  as  aggraded,  in  contrast  to  that  of  a  valley,  which 
is  said  to  be  degraded  ?  9.  What  effect  may  the  aggradation  of  a 
fan  have  in  diverting  rivers  from  their  former  courses  (compare 
the  lower  courses  of  F,  G,  H,  DE,  in  11 1  and  12  2)  ?  in  changing 
the  courses  of  small  streams  (examine  the  small  streams  E.  and 
W-  of  river  DE,  122,  and  compare  them  with  the  corresponding 
streams  in  11 1)  ?  10.  How  may  a  small  stream  be  turned  across  a 
former  divide  by  the  fan  of  a  large  river  (examine  the  first  stream 
W.  of  D,  in  122  and  compare  it  with  ill)?  11.  Which  parts 
of  the  large  river  may  be  said  to  have  a  braided  course  (many 
islands  of  gravel  and  sand,  dividing  it  into  several  channels)  ?  a 
free  meandering  course  in  a  plain  (flowing  in  large  curves,  suit- 
able to  its  large  volume)  ?  12.  Compare  the  fall  of  the  river  in  its 
braided  and  its  meandering  course.]  [13.  The  Hwang-Ho,  a  great 
river  of  China,  flows  out  from  a  gorge  in  the  mountains  upon  a  great 
fan  of  gentle  slope,  where  the  river  course  has  repeatedly  changed. 
Locate  the  river  on  Plate  44.  14.  Why  is  the  river  known  as 


THE  SCULPTURE  OF  "MOUNTAINS          53 

"  China's  Sorrow  "  ?    What  are  the  dimensions  (height  and  radius) 
of  its  fan?  (DE,  265.9-;  DP,  289.2-;   T,  67.6.)] 

12.  1.  Which  parts  of  122  present  forms  due  to  revived  erosion 
following  upwarping  ?  forms  due  to  aggradation  following  down- 
warping  ?  forms  little  changed   from   11 1,    except   for   warping  ? 
2.  Where  can  parts  of  the  former  flood  plain  of  the  main  river  now 
be  seen  in  12  2  ?    3.  Why  is  more  of  the  flood  plain  preserved  near 
the  upper  and  the  lower  ends  of  gorge  CD  than  about  its  middle  ? 
4.  Where  (near  head,  middle  course,  or  lower  course)  are  the  best 
preserved  former  flood   plains  of  the  smaller  rivers  and  branch 
streams  ?    Why  ?    5.  In  what  part  of  these  streams  are  the  deepest 
new-cut  valleys  ?    6.  Why  are  the  new-cut  valleys  less  deep  near 
the  base  of  the  sloping  (upwarped)  upland  than  in  the  mid-slope 
of  the  upland  ?  deeper  at  mid-slope  than  farther  upstream  in  the 
highland  ?   [7.  Why  have  the  small  tributaries  of  the  main  river  in 
gorge  CD  cut  new  valleys  (side  gorges)  of  so  much  greater  depth 
than  the  new-cut  valleys  of  streams  F,  G,  etc.  ?  8.  Examine  16  13. 
To  what  part  of  12  2  does  it  (in  a  general  way)  correspond  ?    9.  Do 
the  side  streams  in  16  13  make  accordant  or  discordant  (hanging) 
junctions  with  the  main  river  ?    10.  Examine  16'14.    To  what  part 
of  12  2  does  it  (in  a  general  way)  correspond  ?    11.  Are  the  stream 
junctions  here  accordant  or  discordant   (hanging)  ?    12.  Explain 
why  accordant  junctions  prevail  in  one  case  and  discordant  junc- 
tions in  the  other.    13.  If  a  large  tributary  joined  the  main  river  in 
the  gorge  CD,  122,  would  the  junction  be  accordant  or  hanging? 
Why?] 

13.  [1.  Locate  a  city  on  the  SW.  lowland  of  12  2 ;  another  on  the 
basin  plain;  some  villages  in  the  NW.  and  in  the  SE.  corners ;  give 
a  name  to  each  city  and  village.    2.  Which  settlements  may  be  most 
easily  connected  by  roads  and  railroads  ?    Why  ?    3.  Mark  dotted 
[red]  lines  to  indicate  roads  from  the  city  on  the  basin  plain  to  the 
other  settlements.   (Avoid  new-cut  valleys  as  far  as  possible ;  if  they 
are  crossed,  the  road  should  be  laid  obliquely  on  the  valley  sides, 
as  in  16  14.)    4.  Draw  a  [red]  line  to  show  a  railroad  connecting 


54  EXERCISES    IN   PHYSICAL   GEOGRAPHY 

the  two  cities,  and  passing  over  the  arched  highland.  (The  rail- 
road must  ascend  the  slope  obliquely.  Why?  If  it  crosses  new- 
cut  valleys,  imitate  the  route  shown  in  16  14.)  5.  Where  would  this 
railroad  cross  the  crest  of  the  highland  in  12  2  to  best  advantage  ? 
Why?  C.  Draw  another  [red]  line  to  show  a  railroad  connecting 
the  two  cities  by  running  through  the  river  gorge.  (Part  of  such  a 
railroad  is  illustrated  in  16  13.)  7.  State  some  of  the  difficulties  and 
some  of  the  advantages  of  each  railroad  route.  8.  Which  parts  of 
12  2  might  be  cultivated  for  lowland  crops  ?  for  highland  crops 
(hardy  grains)  ?  9.  Which  parts  would  probably  remain  forested  ? 
10.  Which  parts  are  exposed  to  floods  ?  11.  Is  the  main  river 
navigable  ?  12.  Which  parts  of  it  are  obstructed  by  many  shoals  ? 
by  rapids  and  low  falls?  (See  16  13.)  13.  The  first  Pacific  railroad 
that  was  built  (1866)  to  connect  the  cities  of  the  eastern  and  cen- 
tral United  States  with  those  on  the  Pacific  slope  crosses  the  high- 
lands of  the  Sierra  Nevada  in  California  ;  its  irregular  route  over  the 
crest  of  the  highland  is  shown  on  the  Colfax,  California,  map,  U.  S. 
G.  S.  14.  A  railroad  in  Colorado  follows  the  Arkansas  river  through 
the  deep,  narrow,  steep-walled  gorge  that  it  has  cut  through  the  Front 
range  of  the  Rocky  mountains.  (See  Canyon  City,  Colorado,  map, 


14.  1.  Note  that  Plate  13  is  passed  by  for  the  present.  Plate  14  is 
in  two  parts,  —  a  SE.  part  (14  3)  and  a  NW.  part  (14  4),  representing 
a  third  and  a  fourth  stage  in  the  history  of  the  district,  of  which  the 
first  and  second  stages  are  shown  in  11  1  and  12  2.  For  the  present 
disregard  14  4.  2.  Compare  the  three-fork  valleys  of  river  G  in  12  2 
and  14  3,  as  to  altitude  of  highland  above  headwaters  ;  depth  of 
new-cut  valleys  (valleys  of  revived  erosion);  sharpness  of  dividing 
ridges  ;  amount  of  neighboring  uncut  upland  or  highland.  [3.  Shade 
lightly  [red]  some  of  the  uncut  uplands  or  highlands  in  143.] 
4.  What  has  happened  since  122  as  to  upwarping?  as  to  erosion 
of  valleys  ?  as  to  destruction  of  highland  surface  ?  as  to  growth 
of  alluvial  fans,?  5.  Which  differences  between  122  and  143 
have  been  produced  by  upwarping  ?  by  erosion  ?  by  deposition  ? 


THE   SCULPTURE   OF   MOUNTAINS  55 

6.  Follow  line  WW,  143,  and  compare  its  course  with  the  corre- 
sponding line  in  12  2.  7.  Draw  a  similar  line  XX,'  14  3.  8.  Why  does 
so  little  uncut  highland  remain  along  this  line  ?  9.  Why  are  the 
ridges  sharp-crested  for  most  of  their  length  ?  10.  Draw  in  16  8 
cross  profiles  for  the  branching  valleys  of  river  G,  14  3,  a  little  S.  of 
line  WW,  and  along  line  A'A".  11.  Compare  the  low  mountains  near 
the  E.  border  of  11 1  with  the  corresponding  parts  of  12  2  and  14  3,  as 
to  change  of  altitude  ;  as  to  change  of  form.  [12.  Draw  profiles 
in  1616  to  illustrate  the  original  (xxx)  and  the  present  (+  ++) 
form  of  these  mountains.] 

15.  1.  The  altitudes  of  points  on  the  line  NN',  14  3,  are  indicated 
in  16  15  by  dots  in  squares ;  of  points  on  neighboring  streams  by 
double  dots.  2.  Draw  in  16 15  the  curve  of  the  upwarped  surface 
(as  if  it  were  uncut)  along  the  line  NN',  14  3  ;  draw  the  profile  of  the 
neighboring  streams.  3.  AY  hat  is  the  average  fall  of  the  S.-flowing 
stream  ?  Why  may  it  be  called  a  torrent  ?  4.  Draw  a  light  [red] 
line  MM',  14  3,  along  the  divide  between  the  N.-flowing  and  the 
S.-flowing  streams.  AYhich  part  of  the  divide  is  sharply  defined  ? 
AYhich  part  is  somewhat  indefinite  ?  Explain.  5.  Compare  this  divide 
with  the  corresponding  divide  in  12  2  as  to  sharpness  ;  as  to  num- 
ber and  steepness  of  its  ascents  and  descents.  6.  Draw  broken  and 
dotted  [red]  lines  along  some  of  the  divides  and  subdivides  of  rivers 
F,  G,  and  H,  14  3,  and  compare  them  with  the  corresponding  divides 
in  11 1  and  12  2,  as  to  sharpness.  7.  Why  are  some  of  the  ridges  and 
mountains  of  14  3  flat-topped  ?  [8.  Certain  ranges  of  the  Tian  Shan 
mountains  in  central  Asia  (locate  on  Plate  44)  have  flat  tops  at  alti- 
tudes of  from  10,000  to  12,000  feet ;  they  are  dissected  by  deep  val- 
leys with  steep  walls,  in  which  the  disordered  structure  of  the  mass 
is  clearly  shown.  A  small  part  of  such  a  range  is  shown  in  14  3  a. 

9.  AYhat  two  processes  have  probably  produced  such  mountains  ? 

10.  The  dissected  slope  between  the  plateau  of  central  France  (NAY.) 
and  the  lowlands  near  the  Mediterranean  (SE.)  is  called  the  Ce- 
vennes  mountains ;  locate  on  Plate  43.    Their  structure  is  greatly 
disordered;   their  ridges  and  spurs  decrease  in  height,  and  their 


56  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

valleys  decrease  in  depth  to  the  SE.;  most  of  the  ridges  have  sharp 
and  narrow  crests,  between  steep-sided,  sharp-V  valleys,  but  some 
of  the  ridges  are  topped  with  even  uplands,  resembling  the  surface  of 
the  (as  yet)  undissected  plateau  farther  NW.  11.  What  shares  have 
warping  and  erosion  had  in  producing  the  Cevennes  ?] 

16.  1.  Why  may  the  name  pass  be  given  to  some  of  the  depres- 
sions in  the  mountain  crest  line  MM',  14  3  ?  2.  How  are  the  passes 
related  to  the  neighboring  valleys  ?  3.  Is  a  pass  found  at  the  head  of 
each  small  branch  of  the  middle  fork  of  river  G  ?  Explain.  4.  Of 
several  neighboring  passes,  which  one  would  be  most  used  ?  Why  ? 
[5.  Draw  a  line  (light  on  first  trial,  heavy  afterwards)  to  show  a  road 
(or  trail)  from  the  southern  lowland,  14  3,  over  the  lowest  pass  in 
the  crest  line  MM'  to  the  inner  basin  BC.  (Where  the  valley  slopes 
are  very  steep,  the  road  (or  trail)  may  have  to  zigzag,  as  in  1622.) 

6.  Draw  a  stronger  line  (light,  at  first)  showing  a  railroad  (see 
16  22)  from  the  fan  of  stream  H,  14  3,  obliquely  ascending  the  slope 
W.  of  valley  H,  and  then  making  its  way  to  the  inner  basin  BC. 

7.  Draw  a  dotted  line  to  show  the  path  by  which  cattle  might  be 
driven   in   summer  from  villages  on  fan  F  to  highland  pastures 
(HP).    8.  What  peculiar  feature  is  seen  in  the  valley  next  NW.  of 
the  highland  pastures  ?     9.  How  may  it  be  related  to  a  lake  ? 
10.  What  disaster  may  happen  when  the  lake  overflows  ?     (DE, 
193.5- ;  DP,  181.5- ;   (7,107.2;  T,  97.4.)]     [11.  Excellent  roads  of 
moderate  grade  have  been  built  over  many  passes  in  the  Alps,  where 
there  is  much  travel  (G,  Fig.  250;   T,  185);  but  in  most  mountains 
the  roads  are  steep  and  rough.    Many  ranges  are  crossed  only  by  nar- 
row trails.    A  railroad  tunnel  (Great  Northern  R.  K.)  passes  under 
the  crest  of  the  Cascade  mountains  in  Washington,  between  the 
upper  parts  of  two  opposite  valleys.    When  the  railroad  was  first 
built  it  ascended  over  the  pass ;  the  tunnel  was  made  afterwards 
to  lessen  the  ascent.    (See  Skykomish,  Washington,  map,  U.  S.  G.  S.) 
Another  line  (Northern  Pacific  R.  R.)  tunnels  through  two  of  the 
Rocky  mountain  ranges  in  western  Montana,  and  through  the  Cas- 
cade mountains  in  Washington.     (See  Livingston,  Montana,  and 


THE  SCULPTURE  OF  MOUNTAINS  57 

Snoqualmie,  Washington,  map,  U.  S.  G.  S.)  Three  long  tunnels  have 
been  cut  under  passes  in  the  Alps,  for  the  passage  of  important 
railroads  from  Switzerland  or  SE.  France  to  N.  Italy  (see  T,  Fig. 
186);  one  of  these  tunnels  (the  Simplon  tunnel)  is  11.9  mi.  long; 
seven  years  (1898-1905)  were  spent  in  cutting  it,  and  it  cost  over 
$16,000,000.] 

17.  1.  Now  examine  14  4  (the  basin  plain  stands  about  1000' 
higher  in  14  4  than  in  14  3)  and  state  the  chief  differences  between 
its  mountain  range  QQ'  and  the  corresponding  parts  of  122,  as  to 
height ;  as  to  form ;  as  to  depth  of  valleys  ;  as  to  ease  of  travel. 

2.  By  what  two  processes  have  these  differences  been  produced  ? 

3.  To  what  process  do  the  mountains  of  14  4  owe  their  altitude  ? 
their  form  ?    4.  Why  is  the  term  sculpture  appropriate  in  connec- 
tion with  the  form  of  such  mountains  ?    5.  What  relation  exists 
between  amount  of  uplift  and  depth  of  sculpture  ?    6.  Draw  a  [red] 
line  along  the  mountain  crest  from  Q  to  Q',  144.    7.  Why  are  none 
of  the  mountains  flat-topped,  like  some  of  the  summits  in  14  3  ? 
8.  Are  the  passes  in  the  range  QQ',  14  4,  easier  or  more  difficult  to 
cross  than  the  passes  in  the  range  MM',  14  3  ?    Explain.    9.  Draw  a 
[red]  line  in  14  4  from  O  at  the  W.  base  of  the  range,  up  the  spur 
ridge,  over  the  peak  0',  and  down  the  spur  ridge  to  O"  at  the  E.  base. 
10.  Where,  on  this  line,  are  parts  of  the  original  upwarped  surface 
least  eroded?    Why?     11.  Draw  a  curved  [red]  line  from  O  to  O" 
to  represent  the  arched  profile  that  the  upwarped  highland  might 
have  had  if  no  erosion  had  taken  place.   (Let  the  crest  of  the  arched 
profile  be  1000'  or  2000'  higher  than  0' ;  see  1620.)    12.  How  much 
upwarping  has  taken  place  here  since  11 1  ?  since  12  2  ?    13.  Com- 
pare the  mountain  profile  0  O'O",  14  4,  with  the  (supposed)  arched 
highland  profile,  as  to  height  ;  as  to  form.    14.  Make  a  statement 
regarding  the   mountains  of  14  4,  similar  to  this  :    "  A   statue   is 
smaller  than  the  block  of  marble  from  which  it  has  been  carved." 
15.  Compare  the  ridges  NN1,  143,  and  0  O'O",  144.    Make  a  state- 
ment regarding  these  ridges,  similar  to  this  :  "  After  a  knife  blade 
is  sharpened  it  is  smaller  than  when  it  was  dull." 


58  EXERCISES  IN  PHYSICAL   GEOGRAPHY 

18.  [1.  Why  is  much  bare  rock  exposed  on  the  peaks,  ridges,  and 
spurs  of  14  4  ?    2.  Why  does  much  coarse  angular  rock  waste  lie  on 
the  slopes  below  the  rock  ledges  ?    3.  Whence  and  how  is  the  waste 
supplied  to  the  slopes?    4.  Why  is  it  coarse  and  angular?    5.  What 
becomes  of  it  ?    6.  Draw  in  16  20  [red]  lines  along  the  divides  and 
subdivides,  and   [blue  lines]  along  the  streams.    7.  How  are  the 
divides  and  subdivides  arranged  with  respect  to  the  stream  and  its 
branches  ?    8.  Where  are  the  streams  steepest  ?    9.  Are  the  stream 
junctions  in  1620  and  in  144  accordant  or  hanging?  Why?  10.  The 
dotted  parts  of  i<>  20  represent  waste-covered  slopes.    Why  may  the 
waste  be  described  as  "  slowly  streaming"?    11.   Select  in  144  a 
spur  extending  from  a  mountain  peak  to  the  mountain  base  ;  shade 
[red]  the  parts  where  bare  ledges  prevail  (see  16  20)  ;  select  an- 
other spur,  and  shade  [blue]  the  waste-covered  slopes.    12.  Where 
is  a  landslide  represented  in  14  4  ?    Why  did  the  landslide  take 
place?    (DE,  193.6;  DP,  181.5 ;   G,  107.2  ;   7',  97.4.)    13.  What  lias 
happened  since  the  slide  took  place  ?    14.  How  high  are  the  walls 
of  the  scar  that  was  left  by  the  slide  ?     About  how  long  is  the 
slide  ?  How  deep  is  the  trench  cut  in  the  slide  ?  How  much  higher 
has  the  lake  (back  of  the  slide)  been  than  it  is  now  ?] 

19.  1.  The  profile  of  the  main  river,  14  4,  is  shown  by  line  AivEiv, 
169.    In  what  parts  of  144  has  the  river  the  strongest  slope  (lay  a 
rule,  or  straight  edge  of  paper,  along  the  profile  ^4ivBiv,  16  9)  ?  the 
most  rapid  current  ?    2.  How  thick  is  the  great  fan  of  the  main 
river  at  the  front  of  144?    3.  Why  does  the  river  now  flow  on  a 
higher  profile  than  in  12  2?   (Compare  profiles  A"E"  and  AivEiv,  16  9.) 
[4.  If  the  river  is  at  a  greater  altitude  than  before,  why  is  the 
gorge  of  14  4  deeper  than  that  of  12  2  ?     5.  What  relation  exists 
between  the  depth  to  which  the  gorge  CD,  144,  has  been  eroded, 
and  the  height  to  which  the  original  surface  has  there  been  up- 
warped  ?    Explain.]     6.   Are  the  junctions    of   side    streams   and 
river,  in  the  gorge,  144,  accordant  or  hanging  ?     [7.  Compare  with 
12  2  and  16  13,  and  explain.    8.  What  does  this  suggest  as  to  the  rate 
of  upwarping  at  the  time  of  14  4,  as  compared  to  rate  at  time  of 


THE  SCULPTURE  OF  MOUNTAINS  59 

12  2  ?]  9.  Estimate  the  thickness  of  the  gravel  and  sand  deposits 
in  the  basin  EC  (see  16  9).  10.  Compare  the  size  of  the  fan  S.  of 
the  mountains  in  14  4  and  12  2.  11.  In  which  figure  may  all  the  fans 
be  described  as  "laterally  confluent"?  Why?  12.  In  which  figure 
may  the  lowland  surface  bordering  the  mountains  be  described  as  a 
"  piedmont  deposit  of  mountain  waste  "  ?  [13.  Compare  the  oppor- 
tunity for  intercourse  and  trade  between  the  people  of  the  W.  plain 
and  the  inner  basin  plain  in  12  2  and  14  4.  14.  Draw  a  dotted  [red] 
line  in  14  4  to  show  (as  much  as  can  be  seen  of)  a  trail  over  the 
mountains,  connecting  the  two  plains.  (Avoid  crossing  the  larger 
streams,  if  you  can  ;  see  the  broken  line,  16  20.)  15.  Describe  a 
trip  on  foot  over  the  range.] 

20.  [1.  37  3  is  a  small  part  of  the  Rocky  mountains  ;  locate  it  on 
Plate  40.  In  what  state  is  it  ?  What  is  the  scale  (miles  to  an  inch)? 
the  contour  interval?  2.  Mark  H  on  the  highest  summit.  What  is 
its  altitude  ?  What  are  the  altitudes  of  several  other  summits?  of 
Conundrum  creek?  3.  How  high  are  the  summits  above  the  creek? 
4.  Are  the  peaks  and  ridges  flat-topped  or  sharp  ?•  5.  What  is  the 
usual  difference  between  peak  and  pass  altitudes  in  the  mountain 
crests?  6.  Draw  a  [red]  line  along  the  crest  of  each  mountain 
ridge  in  this  figure;  broken  [red]  lines  from  the  crest  down  several 
spurs.  7.  Mark  S  on  a  short  spur  that  ends  between  the  forks 
of  a  branch  of  Conundrum  creek  ;  L  on  a  long  spur  that  extends 
without  dividing  from  the  mountain  crest  to  Conundrum  creek ;  D 
on  the  separate  lower  ends  (or  spurlets)  of  a  spur  that  is  divided 
by  short  branches  of  Conundrum  creek.  8.  Print  5  on  a  spur  that 
divides  into  five  spurlets;  print  6  on  a  slope  that  is  divided  into 
six  short  spurs  between  the  forks  of  one  branch  of  Conundrum 
creek.  9.  Draw  a  dotted  [red]  line  to  show  a  trail  from  some 
point  on  Conundrum  creek  to  the  W.  border  of  the  map.  10.  How 
did  you  determine  where  the  trail  should  cross  the  W.  range  ?  11.  Is 
the  sculpture  of  these  ranges  farther  advanced  than  the  sculpture 
of  the  mountains  in  37  1  and  372?  How  can  you  tell?  12.  Of 
these  three  mountains,  which  would  you  describe  as  maturely 


60  EXERCISES  IX  PHYSICAL  GEOGRAPHY 

dissected  ?  which  as  in  an  early  (young)  stage  of  its  cycle  of  ero- 
sion ?  13.  374  is  part  of  the  San  Antonio  mountains;  locate  on 
Plate  40.  In  what  part  of  what  state  is  it?  What  is  the  scale? 
the  contour  interval  ?  14.  What  is  the  greatest  altitude  shown  ? 
15.  Is  the  dissection  immature  or  mature  ?  16.  Compare  in  37  3  and 
37  4  the  pattern  of  the  contours  ;  the  size  of  the  spurlets.  In  which 
of  these  two  maps  might  the  dissection  of  the  mountains  be 
described  as  of  finer  texture  ?  17.  Describe  the  form  of  the  S.  part 
of  37  4.  Explain  its  origin.  What  name  is  given  to  such  forms  ? 
Where  does  a  similar  form  occur  in  14  4  ?  18.  The  basin  plain  or 
"  vale  "  of  Kashmir  lies  between  the  outer  and  the  inner  ranges 
of  the  lofty  Himalaya  mountains  in  NW.  India;  locate  it  on 
Plate  44.  It  is  100  mi.  long  by  50  mi.  wide,  and  5000'  above  sea 
level  ;  the  passes  in  the  inclosing  mountain  range  have  an  altitude 
of  over  10,000'.  The  vale  is  occupied  by  a  people  who  differ  in 
various  ways  from  the  people  of  the  outer  piedmont  plains.  19.  The 
river  Jhelam  flows  from  the  inner  basin  plain  through  a  deep,  nar- 
row, steep-walle'd  gorge  in  the  inclosing  mountains  to  the  outer 
plains  ;  the  native  people  have  therefore  crossed  the  inclosing 
range  for  centuries  only  by  a  high  pass  ;  in  recent  years  British 
engineers  have  built  a  road  part  way  through  the  gorge.  (DP, 
284.6-.)  20.  Point  out  some  similar  features  in  14  4.] 

21.  Now  turn  to  Plate  13.  NOTE  :  13  5  and  13  6  represent  later 
stages  of  the  district  already  studied  in  11 1  to  14  4;  for  the  present  do 
not  consider  136.  1.  Compare  the  W.  range  in  144  and  135  as  to 
height ;  as  to  sharpness  of  peaks,  ridge  crests,  and  spurs  ;  as  to  slope 
of  valley  sides  ;  as  to  steepness  of  stream  profiles.  Explain  the  dif- 
ferences. 2.  Which  one  of  these  two  ranges  has  the  greater  amount 
of  bare  ledges?  of  waste-covered  surface?  (See  16  19  and  1620,  in 
which  the  waste-covered  surface  is  dotted.)  3.  By  what  process 
can  you  account  for  the  differences  ?  4.  When  did  the  greater 
amount  of  upwarping  take  place,  between  12  2  and  14  4  or  between 
14  4  and  13  5  ?  5.  Why  may  the  waste-covered  slopes  in  is  5  be 
described  as  "  graded  "  ?  the  bare  rock  ledges  as  "not  yet  graded"? 


THE   SCULPTURE  OF  MOUNTAINS  61 

the  rounded  summits,  crests,  and  spurs  as  "  subdued  "  ?  (DE,  204.8- ; 
DP,  187. 1-.)  6.  Draw  in  the  upper  part  of  16  17  a  cross  profile  of 
the  spurs  and  valleys  on  the  line  XX',  13  5.  7.  Compare  it  with  pro- 
file A' A*',  16  8,  and  explain  the  differences.  8.  Compare  the  main 
river  in  14  4  and  13  5  as  to  altitude  at  ^4  and  E  ;  as  to  fall  and 
velocity  from  A  to  E  ;  as  to  amount  and  texture  of  waste  received 
from  tributaries.  9.  In  a  river  of  given  volume  what  relation  exists 
between  its  load  (amount  and  texture  of  waste)  and  the  slope  to 
which  it  may  wear  down  its  profile  ?  (DE,  254.9  ;  DP,  243.2.) 
10.  Why  have  the  rivers  of  13  5  begun  to  degrade  the  alluvial  fans 
and  plains  that  they  previously  aggraded  ?  NOTE  :  The  remaining 
parts  of  the  fans  and  plains  (dotted  in  12  2,  14  3,  and  14  4)  are 
unshaded  in  135.  11.  What  features  in  the  valley  CD,  is  5,  indi- 
cate whether  the  river  is  or  is  not  still  deepening  its  valley  ? 
Explain.  12.  Why  was  not  the  widening  of  the  valley  bottom 
begun  at  an  earlier  stage  (as  in  12  2  or  14  4)  ?  13.  What  can  you 
infer  from  this  as  to  whether  the  warping  and  uplift  of  the  region 
is  still  going  on  or  not  ?  [14.  The  Black  mountains  of  North  Caro- 
lina possess  many  of  the  features  here  described.  Their  summits, 
ridges,  and  spurs  are  rounded ;  their  slopes  are  graded,  with  few 
cliffs  or  ledges  ;  their  valleys  are  usually  open ;  their  streams 
commonly,  have  narrow  flood  plains.] 

22.  [1.  What  features  in  16  10  indicate  that  the  river  has  been 
cutting  laterally  (sideways)  as  well  as  downwards  during  the 
erosion  of  its  gorge  ?  2.  Draw  a  full  [or  red]  line  along  the  outer 
bank  of  each  river  curve  (or  meander)  in  1C  10,  11,  12 ;  draw  a 
dotted  [or  blue]  line  along  the  inner  bank  of  each  curve.  3.  Are 
the  dotted  [or  blue]  lines  all  on  the  same  side  of  the  river  ?  How 
are  they  arranged  ?  4.  Let  the  steeper  parts  of  the  gorge  wall  be 
called  the  undercut  slopes,  or  undercut  amphitheaters;  shade  them 
lightly  [red].  5.  Call  the  less  steep  parts  the  slip-off  slopes,  or  slip- 
off  spurs ;  dot  them  [blue].  6.  Explain  why  the  preceding  terms 
are  appropriate.  7.  What  relation  exists  in  16  10  between  the  outer 
bank  of  a  river  curve  and  the  undercut  slopes  ?  between  the  inner 


62  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

bank  and  the  slip-off  slopes  ?  8.  In  which  one  of  16  10,  11,  12,  is 
the  river  bordered  by  narrow  flood-plain  scrolls  ?  by  wider  flood- 
plain  scrolls?  9.  Where  are  the  flood-plain  scrolls  situated  with 
respect  to  the  inner  and  outer  banks  of  the  river  curves  (or 
meanders)  ?  with  respect  to  the  undercut  slopes  ?  to  the  slip-off 
slopes?  10.  In  1G  10,  11,  12,  draw  a  nearly  straight  line  touching 
the  river  curves  on  the  right ;  another  on  the  left.  11.  The  space 
included  between  each  pair  of  lines  may  be  called  the  meander  belt. 
How  does  its  width  change?  12.  During  the  erosion  of  the  gorge, 
16  10,  which  was  greater,  downward  river  erosion  or  lateral  river 
erosion  ?  13.  During  the  development  of  the  flood-plain  scrolls, 
16  11,  16  12,  which  was  greater,  downward  or  lateral  river  erosion  ? 
14.  If  the  downward  erosion  (or  deepening)  of  the  gorge  resulted 
from  the  revival  of  river  erosion  by  the  upwarping  of  its  district, 
does  the  upwarping  still  continue  or  has  it  ceased,  now  that  flood 
plains  are  developing  ?] 

23.  [1.  Shade  [light  red]  three  undercut  slopes  on  the  W.  side 
of  the  main  river  gorge  CD,  13  5 ;  three  on  the  E.  side.  2.  Mark 
with  [light  blue]  dots  three  slip-off  slopes,  or  spurs,  on  each  side  of 
the  gorge.  3.  Shade  [light  red]  three  flood-plain  scrolls  on  each 
side  of  the  river  in  the  gorge.  4.  Are  the  flood-plain  scrolls  on  the 
up-valley  side  or  the  down-valley  side  of  the  spurs  ?  5.  Why  may  the 
spurs  that  adjoin  the  flood-plain  scrolls  be  described  as  "trimmed 
on  the  up-valley  side  "  ?  (See  also  16  21,  looking  across  a  valley.) 
6.  Why  may  the  spurs  on  the  farther  side  of  the  valley,  16  18,  be  de- 
scribed as  "  nearly  consumed "  ?  7.  With  which  stage  of  flood- 
plain  development,  as  shown  in  16 11  (narrow  flood-plain  scrolls), 
16  12  or  21  (broad  flood-plain  scrolls),  and  16  18  (broad  flood-plain 
lobes},  do  the  flood  plains  in  the  gorge  of  13  5  best  correspond  ? 
8.  With  which  stage  of  spur  erosion,  as  shown  in  1611  (little- 
trimmed  spurs),  16  12  or  21  (well-trimmed  spurs),  and  16  18  (nearly 
consumed  spurs),  do  the  spurs  in  the  gorge  of  13  5  best  correspond  ?] 
[9.  Draw  in  13  5  a  broken  [red]  line  to  show  a  road,  and  a  full  [red] 
line  to  show  a  railroad,  crossing  the  W.  mountain  range.  (See 


THE  SCULPTURE  OF  MOUNTAINS  63 

16  19  ;  the  road  is  here  a  single  line,  the  railroad  a  double  line.) 
10.  Draw  a  [red]  line  to  show  a  railroad  following  one  side  of  the 
valley  CD,  135.  11.  What  part  of  this  railroad  would  have  to  be 
built  on  steep  slopes  ?  12.  A  railroad  of  this  kind  follows  the  deep 
meandering  valley  of  the  N.  branch  of  the  Susquehanna  river  in 
Pennsylvania ;  another  follows  the  similar  valley  of  the  Mosel  river 
in  W.  Germany.  (DP,  254.5.)] 

24.  1.  Examine  13  6  and  compare  it  with  13  5,  as  to  altitude  ;  as 
to  relief  ;  as  to  steepness  of  hillside  (or  valley-side)  slopes ;  as  to 
breadth  of  flood  plains  along  small  streams.  2.  Explain  the  differ- 
ences. 3.  Which  has  been  the  more  important,  warping  or  erosion, 
in  causing  the  change  from  11 1  to  12  2  ?  from  13  5  to  13  6  ?  [4.  In 
14  3  and  14  4  which  is  the  more  rapid,  the  deepening  of  the  valleys 
or  the  wearing  down  of  the  peaks  ?  5.  Answer  the  same  question 
for  13  5  and  13  6.  6.  Explain  the  difference  between  the  answers  to 
these  two  questions.  7.  Is  the  wearing  down  of  the  summits  faster 
in  14  4  or  in  13  6  ?  8.  What  conclusion  is  suggested  by  answers  to 
questions  5  and  7,  as  to  the  rate  of  valley  deepening  in  13  6  ? 
9.  Would  you  expect  bare  rock,  thin  soil,  or  deep  soil  on  the  sharp 
divides  of  14  4  ?  on  the  rounded  divides  of  13  5  ?  on  the  low  divides 
of  13  6  ?]  10.  Draw  in  the  middle  of  16  17  a  profile  on  XX',  13  6 ; 
draw  below  this  another  profile  representing  a  later  stage  of  ero- 
sion than  13  6 ;  below  this  again  a  still  later  stage.  11.  In  what 
way  do  these  three  profiles  differ?  12.  Would  the  change  from 
one  to  the  other  be  quickly  or  slowly  produced  ?  Why  ?  13.  When 
the  district  here  studied  reaches  a  later  stage  of  erosion  than  is 
shown  in  13  6,  which  one  of  the  figures  11 1  to  13  5  will  it  most 
resemble  ?  14.  What,  then,  is  the  probable  explanation  of  the  forms 
shown  in  ill?  15.  Such  a  district  may  be  called  a  peneplain  (that 
is,  almost  plain).  16.  What  relation  has  a  peneplain  to  baselevel  ? 
to  the  underlying  rock  structures  (such  as  are  shown  in  the  front 
sections  of  16  13  and  16  20)  ?  17.  Suppose  that  part  of  a  district  like 
the  one  here  considered  consisted  of  much  more  resistant  rocks 
than  the  rest.  What  features  would  you  expect  to  survive  in  the 


64  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

area  of  the  very  resistant  rocks,  when  the  less  resistant  parts  were 
worn  down  to  a  peneplain  ?  18.  In  which  figure  of  this  series 
are  such  features  represented  ?  NOTE  :  Such  residual  hills  or  low 
mountains  may  be  classed  as  monadnocks.  (DE,  207.6  ;  DP,  190.1; 
G,  87.9  ;  T,  298.6.)  19.  If  a  seventli  figure  were  drawn,  represent- 
ing a  later  stage  than  13  6,  where  would  you  expect  to  see  a  group 
of  monadnocks  ?  [20.  How  do  the  monadnocks  in  12  2  differ  from 
those  in  11 1  ?  21.  A  large  area  in  W.  Siberia  around  Omsk  is  a 
peneplain  of  small  relief,  with  occasional  monadnocks.  Between 
what  mountains  does  this  peneplain  lie?  by  what  river  is  it  drained? 
(See  Plate  44.)] 

25.  [1.  What  two  unlike  processes  are  concerned  in  a  "cycle  of 
erosion  "  ?  NOTE  :  Let  the  successive  stages  of  a  cycle  of  erosion 
be  called  "early  youth,"  "youth,"  "early  maturity,"  "full  matur- 
ity," "  late  maturity,"  "  early  old  age,"  "  late  old  age."  2.  Which 
of  these  terms  may  be  used  in  describing  the  figures,  12  2  to  13  6  ? 
3.  Does  11 1  belong  in  the  same  cycle  of  erosion  with  the  following 
figures  ?  4.  What  sort  of  movement  interrupted  the  cycle  of  the 
first  figure  and  introduced  the  cycle  of  the  later  figures  ?  5.  In 
what  stage  was  ill  when  its  cycle  of  erosion  was  interrupted? 
6.  In  the  early  youth  of  a  new  cycle  which  parts  of  the  surface 
preserve  forms  little  changed  from  the  old  age  (peneplain)  of  a 
previous  cycle  ?  7.  In  the  stage  of  full  maturity  (strongest  relief 
and  greatest  variety  of  form),  how  would  the  divides  differ  from 
their  form  in  youth  ?  from  their  form  in  old  age  ?  8.  How  would 
the  load  of  the  rivers  differ  in  maturity  and  in  old  age  ?  9.  How 
would  the  streams  of  youth  differ  from  those  of  old  age  as  to 
slope  ?  as  to  the  occurrence  of  falls  and  rapids  ?  10.  Which  stage, 
youth,  maturity,  or  old  age,  occupies  the  longest  time  in  a  com- 
pleted cycle  of  erosion  ?  11.  Is  it  necessary  that  a  cycle  of  erosion 
should  continue  without  interruption  (by  uplift,  warping,  or  depres- 
sion) until  late  old  age  ?  12.  Suppose  that  interruption  by  uplift 
occurred  at  the  stage  of  13  5 ;  describe  the  forms  of  the  district 
in  a  young  stage  of  the  new  cycle  of  erosion  thus  introduced. 


THE  SCULPTURE  OF  MOUNTAINS  65 

13.  What  features  would  you  expect  in   a  region  that  had  been 
worn  down  to  a  peneplain  (with  a  few  monaduocks)  in  a  long, 
undisturbed  cycle  of  erosion,  and  that  had  then  reached  early  ma- 
turity in  a  new  cycle  introduced  by  a  broad  uplift  of  GOO'  or  800'  ? 

14.  The  Appalachian  Piedmont  belt  of  Virginia,  the  Carolinas,  and 
Georgia  (locate  it ;  see  DE,  Fig.  100 ;  DP,  Fig.  117)  is  such  a  region  ; 
many  other  examples  of  peneplains,  upwarped  and  more  or  less  dis- 
sected, might  be  mentioned.    15.  Locate  37  5  on  Plate  40.    16.  What 
is  the  general  altitude  of  the  uplands  ?    17.  How  much  higher  is 
Stone  mountain  than  the  uplands  ?    18.  How  deep  are  the  valleys 
below  the  uplands  ?   19.  The  uplands  are  part  of  the  uplifted  Appa- 
lachian Piedmont  peneplain.    How  many  cycles  of  erosion  are  here 
represented  ?    20.  What  stage  had  the  first  cycle  reached  when  it 
was  interrupted  by  regional  uplift  ?    How  can  you  tell  ?    21.  What 
stage  has  now  been  reached  in  the  new  cycle  of  erosion  ?    How 
can  you  tell  ?    22.  What  term  already  used  would  apply  appropri- 
ately to  Stone  mountain  ?    23.  Make  a  list  of  the  features  which 
characterize  the  youthful  stage  in  a  cycle  of  erosion ;  the  mature 
stage  ;  the  old  stage.] 

26.  Define  :  §  1,  interfluve ;  §  2,  well-defined  divides,  ill-defined 
divides  ;  §  4,  an  arched  or  upwarped  district,  [river  beheaded  by 
warping,]  torrent  ;  §  5,  revived  or  rejuvenated  stream,  sharp  V- 
shaped  valley  ;  §  8,  basin  plain,  bent-down  or  down-warped  basin  ; 
§  9,  antecedent  river  ;  §  10,  river  diverted  by  warping,  beheaded 
by  warping  ;  §  11,  alluvial  fans,  laterally  confluent  (alluvial)  fans, 
aggrade,  aggradation,  degrade,  degradation,  braided  river  coarse, 
meandering  river  course  ;  §  16,  pass  ;  §  17,  mountain  sculpture  ; 
[§  18,  landslide  ;]  §  21,  subdued  mountains  ;  [§  22,  undercut  slopes, 
slip-off  slopes,  flood-plain  scrolls,  meander  belt ;  §  23,  trimmed  spurs, 
flood-plain  lobes  ;]  §  24,  peneplain,  residual  mountain,  inonadnock ; 
[§  25,  interruption  of  a  cycle  of  erosion]. 


EXERCISE  VI.     VOLCANOES  AND  LAVA  FLOWS 

OBJECT.  To  illustrate  the  various  forms  of  volcanoes  and  lava  flows, 
and  the  effects  that  they  produce  on  land  sculpture  by  rivers. 

Preliminary.  17  1  to  19  8  of  this  exercise  represent  the  same  piece 
of  country  (shown  as  a  block,  cut  out  from  its  surroundings),  at 
different  stages  in  the  history  of  a  group  of  volcanoes  and  their 
associated  features.  The  NW.  and  SE.  corners  of  the  figures  are 
cut  off  to  save  space.  The  complete  block  would  measure  about 
4  mi.  N.-S.  by  5  mi.  E.-W.  Scales  of  miles  are  marked  on  the  S. 
and  W.  baselines  ;  a  scale  of  altitudes  (feet)  is  given  on  the  SW. 
corner.  The  numbers  on  the  upland  indicate  altitudes  in  feet  above 
sea  level.  Plates  17, 18,  20,  19,  and  15  are  used  in  this  exercise  [also 
38  3].  Note  that  Plate  20  is  to  be  used  before  Plate  19. 

1.  1.  What  is  the  general  altitude  of  the  upland  in  17  1  ?  its  gen- 
eral measure  of  relief  (general  height  of  uplands  over  valley  floors)  ? 
(The  uplands  are  not  level,  but  slope  gently  toward  the  valley  sides, 
as  shown  on  the  S.  border  of  the  block.)    2.  What  is  the  average 
fall  of  river  UV  in  feet  per  mile  ?    (Use  scale  on  W.  baseline  for 
river  length.)    3.  What  is  the  altitude  of  the  pass  A'  between  the 
valleys  of  river  UV  and  of  river   YY'?    4.  Draw  a  dotted  [red] 
line  along  the   divide  between  the   V  and  the   Y  river   systems. 
5.  Draw  a  [pencil]  line  on  a  direct  path  from  C  to  C";  from  D  to 
D'.    (Follow  the  heavy  hachure  lines  downhill  and  uphill.)    6.  Draw 
to  scale  in  15  9  a  cross  profile  of  UV  valley  at  CC'  and  DD'. 

2.  1.  What  are  the  three  chief  events  that  have  taken  place  in  the 
change  from  17  1  to  17  2  ?    2.  What  is  the  height  of  the  volcano  sum- 
mit above  sea  level  in  17  2  ?  above  the  neighboring  upland  ?   the 
diameter  of  its  base   (use   scale  on   S.  baseline)  ?    of  its  crater  ? 
[3.  What  is   (roughly)  the  volume  of  the  volcano  ?     NOTE  :    The 

66 


VOLCANOES  AND  LAVA   FLOWS  67 

volume  of  a  cone  =  area  of  base  x  -J-  height ;  the  area  of  the  (circu- 
lar) base  =  2>\  x  square  of  radius.]  4.  Why  did  the  lava  flow  turn 
S.  in  UV  valley?  5.  Is  the  lava  flow  higher  along  its  middle  or 
along  its  sides  ?  6.  What  effect  has  the  flow  had  upon  the  position 
of  the  junction  of  river  ZZ  with  river  UV?  7.  What  is  the  length 
of  the  flow  (use  scale  on  W.  baseline)  ?  average  breadth  of  flow  (use 
scale  on  S.  baseline)?  thickness  of  flow  at  mid-length?  (In  an- 
swering the  last  question  compare  altitude  of  flow  surface  in  17  2 
with  altitude  of  corresponding  points  in  valley  floor,  17  1.)  [8.  What 
is  (roughly)  the  volume  of  the  flow  ?  NOTE  :  Multiply  length  x 
average  breadth  x  \  average  thickness  along  valley  line.  9.  Which 
has  the  greater  volume,  the  cone  or  the  flow  ?] 

3.  1.  Why  have  several  lakes  been  formed  in  17  2  ?    2.  Determine 
the  length,  breadth,  and  greatest  depth  of  lake  A.    3.  Why  is  the 
outlet  of  lake  A  along  the  W.  side  (instead  of  the  E.  side)  of  the 
lava  flow  ?    4.  If   the  altitude  of  lake  C  is  1900',  what  is  the  aver- 
age fall  of  river  £7Fin  feet  per  mile  from  the  lake  to  the  end  of  the 
flow  ?    5.  Why  is  this  average  fall  greater  than  that  of  river  UV  in 
17  1  ?    G.  Why  has  a  narrow  gorge  been  cut  along  the  W.  side  of 
the  lava  flow  of  17  2  between  lakes  A  and  C  ?    Why  has  a  gorge 
been  cut  on  each  side  of  this  lava  flow  near  its  end  ?    7.  Why  is 
there  no  gorge  along  the  E.  side  of  the  lava  flow  near  F1  ?    8.  Esti- 
mate the  breadth  and  depth  of  each  gorge.    9.  Draw  a  [pencil]  line 
on  a  direct  path  from  E  to  E',  crossing  lake  A  and  going  over  the 
volcano;  from  F  to  F';  from  G  to  G'.    [10.  In  15  10  draw  cross  sec- 
tions for  the  three  profiles,  showing  in  EE'  the  bottom  of  the  lake, 
the  base  of  the  volcano,  and  the  passage  or  pipe  up  through  which 
the  lava  neck  rose  from  its  deep  source ;  in  FF'  the  base  of  the  lava 
flow,  and  the  old  and  new  course  of  river  UV;  in  GG1  the  base  of 
the  flow,  and  the  larger  and  smaller  gorges.] 

4.  [1.  A  small  volcano  called  Monte  Nuovo  (New  Mountain)  was 
formed  by  sudden  eruption  on  the  N.  border  of  the  gulf  of  Naples 
in  1538.    (DE,  218.6;   DP,  202.G ;    T,  Fig.  207.)    2.  To  what  does 
Monte  Nuovo  correspond  in  172?    In  what  part  of  Italy  is  it? 


68  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

(See  Plate  43.)  3.  A  smooth  cinder  cone  in  California  is  believed  to 
have  been  erupted  about  200  years  ago ;  a  younger  lava  flow  near 
the  cone  produced  Snag  lake,  so  called  because  the  dead  trunks  of 
trees  that  grew  before  the  eruption  are  still  to  be  seen  there.  (DE, 
219.8;  DP,  203.8;  also  J.  S.  Diller,  Bull.  79,  U.S.G.S.;  good  de- 
scription and  many  excellent  plates.)  4.  To  what  do  these  features 
correspond  in  17  2  ?  In  what  part  of  California  is  Snag  lake  ?  (See 
Plate  40.)  How  far  and  in  what  direction  from  Mt.  Shasta  ?  5.  In 
1759  the  volcano  Jorullo  (pron.  Ho-rul-yo),  in  Mexico,  was  rapidly 
built  of  lava  and  cinders,  its  crater  rim  rising  about  700'  over  the  lava 
flows  around  its  base  ;  fine  cinders  or  ashes  and  dust  were  showered 
on  the  cone,  the  flows,  and  the  surrounding  country.  6.  Locate 
Jorullo  on  Plate  41.  How  far  and  in  what  direction  is  Jorullo  from 
Popocatapetl  ?  The  cone,  lava,  and  ashes  of  Jorullo  were  barren  for 
many  years,  but  they  are  now  more  or  less  covered  with  vegetation. 
(DE,  219.1;  DP,  203.1.)  7.  Lava  flows,  cascading  down  high  cliffs 
in  Arizona,  are  shown  in  Atlas,  sheet  V,  of  U.S.G.S.,  Monogr.  II 
(copied  (in  part)  in  DE,  Fig.  113;  DP,  Fig.  129).  8.  Where  was 
a  lava  cascade  formed  in  change  of  17  1  to  17  2  ?] 

5.  1.  15  11  is  a  map,  partly  in  100'  contours,  partly  in  hachures,  of 
a  volcano,  its  lava  flows  and  a  portion  of  the  surrounding  country ; 
the  contours  are  dotted  on  the  non-volcanic  surface ;  the  scale  is 
1 : 62,500.  2.  What  is  the  diameter  of  the  cone  at  its  base  ?  the 
height  of  the  cone  above  the  hilly  upland  ?  [the  angle  of  slope 
of  its  sides  ?]  3.  Draw  [red]  lines  along  the  middle  of  each  flow, 
and  shade  lightly  [red]  the  surface  of  the  cone  and  flows.  4.  Why 
does  the  E.  flow  widen  where  its  mid-line  is  1650'?  5.  About  how 
much  higher  is  the  mid-line  of  the  E.  flow  than  its  N.  border  ?  than 
its  S.  border  ?  6.  What  is  the  average  fall  along  the  mid-line  ? 
NOTE  :  The  lava  of  flows  as  steep  as  those  here  shown  must  have 
been  viscous  when  erupted ;  the  more  fluid  the  lava,  the  less  the 
slope  of  the  flows  when  they  solidify.  7.  Draw  dotted  [blue]  lines 
to  represent  the  (probable)  stream  courses  before  the  volcano  was 
formed.  8.  Shade  [light  blue]  the  four  small  lakes.  Why  were  they 


VOLCANOES  AND  LAVA  FLOWS  69 

formed  ?  9.  Mark  O  at  the  lake  outlets.  10.  What  is  the  altitude 
of  the  outlets  ?  11.  Draw  full  [blue]  lines  to  represent  the  present 
streams,  and  darken  the  lines  where  gorges  will  be  cut.  12.  Why 
is  a  single  former  stream  now  represented  by  two  streams  for  part 
of  its  length  ?  [13.  Estimate  the  thickness  of  the  E.  flow  where  its 
mid-line  is  1400',  1700',  1800',  and  2000'.  14.  In  what  part  of  the 
flow  is  its  thickness  greatest,  —  close  to  base  of  cone,  midway  along 
the  flow,  or  near  end?  Why  ?]  [15.  Draw  in  is  12,  scale,  1 :  62,500, 
with  100'  contours,  a  volcano  2100'  altitude  at  r,  with  lava  flows 
extending  E.  and  SW.  (The  numbers  by  crosses  (x)  indicate  alti- 
tudes at  middle  and  side  of  the  flows.)  16.  Indicate,  as  above,  the 
drainage  before  and  after  eruption.  17.  Mark  O  at  the  outlets  of 
the  several  lakes.  (Some  of  the  outlets  are  close  along  the  lava 
flows ;  one  is  across  a  divide  between  former  streams,  like  X,  n  2.) 
18.  Shade  the  lakes  [light  blue],  and  draw  dark  [blue]  lines  where 
gorges  will  be  cut.  19.  What  is  the  angle  of  slope  of  cone  ?  length, 
breadth,  greatest  thickness,  and  fall  per  mile  of  mid-line  of  each 
flow?  length,  breadth,  and  greatest  depth  of  each  lake?  20.  Draw 
lines  to  show  the  former  [dotted  red]  and  the  present  [full  red] 
divide  between  the  NE.  and  the  SW.  river  systems.] 

6.  1.  What  are  three  chief  differences  between  17  2  and  18  3 
directly  due  to  volcanic  eruption?  2.  What  has  happened  in  183 
to  lake  B  of  17  2  ?  Explain.  3.  What  is  the  altitude  of  the  W. 
border  of  the  large  new  lava  flow  near  H,  18  3  ?  4.  How  much 
higher  is  the  surface  of  lake  A  in  183  than  in  172?  Why  is  it 
higher  ?  5.  To  what  river  does  lake  A  overflow  in  18  3  ?  6.  Ex- 
plain this  change  from  17  2.  7.  How  much  higher  has  lake  A  been 
than  it  is  now  ?  (See  X,  17  2.)  8.  What  new  feature  has  been 
produced  along  the  outlet  of  lake  A  in  18  3  ?  Explain.  9.  Draw  a 
[blue]  line  along  the  outlet  stream  of  the  two  small  lakes  W.  of 
the  lava  flow  in  is  3.  10.  Why  does  the  outlet  stream  follow  this 
course?  11.  Draw  a  [red]  line  in  18 3  along  the  divide  between 
river  systems  VZ  and  Y'.  12.  Why  does  this  line  differ  from  the 
corresponding  line  in  17  1  ?  13.  Compare  the  volume  of  river  V  at 


70  EXERCISES  IN   PHYSICAL  GEOGRAPHY 

the  S.  border  of  17  1,  172,  183;  of  river  Y'  at  E.  border  of  each 
figure.  Explain  the  changes.  14.  In  18  3  why  is  the  gorge  of  river 
Z  deeper  than  the  gorge  of  river  F?  15.  Draw  a  [pencil]  profile 
line  in  18  3  from  H  directly  across  the  newer  lava  flow,  over  both 
volcano  summits,  to  //';  from  -/  across  both  lava  flows  to  ./';  from 
K  to  K'.  [16.  In  15  10  draw  cross  sections  corresponding  to  these 
profiles,  and  show  in  section  ////'  the  bottom  of  the  newer  lava  flow, 
the  base  of  both  volcanoes,  and  the  pipes  by  which  the  lava  has 
risen  ;  in  sections  .7.7'  and  KK',  the  surface  and  bottom  of  each  flow, 
the  newer  one  burying  the  gorge  previously  eroded  along  the  W. 
border  of  the  older  one  (see  17  2).]  [17.  AVhat  large  lake  in  Central 
America  is  due  to  a  volcanic  barrier?  (DE,  231. 9-.)  Locate  this 
lake  on  Plate  41.  18.  What  river  has  thus  been  made  to  flow  across 
the  former  "  continental  divide  "  between  the  Atlantic  and  Pacific 
oceans  ?  Explain.] 

7.  1.  What  are  the  chief  changes  from  18  3  to  184  as  to  vol- 
canoes ?  as  to  lava  flows  ?  as  to  lakes  ?  as  to  lake  outlets  ?  (Lake 
Y  and  river  Y'  are  separated  by  a  divide,  2900',  on  the  NE. 
border  of  the  NE.  lava  flow.)  2.  What  is  the  height  of  the  great 
volcano  above  the  uplands  around  its  base  ?  the  diameter  of  its 
base  ?  [its  volume,  compared  to  that  of  the  volcano  in  17  2  ?] 
3.  What  change  has  taken  place  in  the  form  of  the  larger  vol- 
cano of  18  3  ?  4.  Explain  why  it  may  now  be  called  a  "  dissected 
volcano."  5.  What  has  become  of  the  smaller  volcano  of  18  3  ? 
6.  Why  are  the  ravines  of  so  moderate  a  depth  on  the  slopes  of  the 
great  volcano,  18  4  ?  (Many  ravines,  eroded  to  a  considerable  depth 
while  the  volcano  was  smaller,  may  have  been  filled  with  lava  and 
ashes  by  later  eruptions.)  [7.  Fujiyama,  a  great  volcano  in  Japan 
(between  Tokyo  and  Kyoto ;  locate  on  Plate  44)  is  a  nearly  symmet- 
rical cone  rising  about  14,000'  close  to  the  seacoast ;  its  slopes  are 
but  moderately  dissected  by  radiating  ravines.  In  what  part  of 
what  island  is  this  volcano  ?  8.  Mt.  Shasta  is  a  large  volcano  of 
similar  height  in  California.  (DE,  229.9- ;  DP,  214.1 ;  G,  211.9 ;  T, 
121.5  ;  also  J.  S.  Diller,  Nat.  Geogr.  Monogr.  No.  8.)  9.  In  what 


VOLCANOES  AND  LAVA   FLOWS  71 

part  of  California  is  Mt.  Shasta  ?  (See  Plate  40.)  What  is  its  alti- 
tude ?  Compare  its  dissection  with  that  of  the  larger  and  smaller 
volcanoes  of  18  4.] 

8.  1.  How  many  lava  flows  are  shown  in  is  4  around  the  base  of 
the  great  volcano?    2.  What  is  the  relative  age  of  the  SW.,  S., 
and  SE.  flows  ?    Explain.    3.  How  many  different  lava  flows  are 
shown  on  17  2,  18  3,  and  18  4  ?    (Include  the  two  small  flows  in  the 
center  of  is  3,  and  the  several  larger  flows  shown  in  section  on  the 
S.  face  of  18  4.)    4.  What  is  the  total  thickness  of  the  four  flows 
shown  in  section  on  the  S.  face  of  18  4  ?    5.  Why  is  the  under  sur- 
face of  these  flows  uneven  ?     [6.  How  can  you  estimate  (roughly) 
the  relative  duration  of  the  time  intervals  between  the  outpouring 
of  these  four  flows  ?    7.  Were  they  about  equal  or  very  unequal  ?] 
NOTE  :  The  flows  that  issue  from  the  flanks  of  a  volcano  (as  here 
or  SW.,  S.,  and  SE.)  are  probably  supplied  through  great  under- 
ground fissures,  splitting  the  earth's  crust  outward  from  the  cen- 
tral pipe  of  the  cone.    The  lava  that  solidifies  underground  in  such 
fissures  forms  dikes.     [8.  Numerous  barren  lava  flows  are  found 
around  the  volcanoes  of  Mexico.    The  surface  of  the  lava  is  often 
so  rough  as  to  be  nearly  impassable.    Why  ?    (DE,  227.7 ;    DP, 
209.8 ;  G,  198.7.)    9.  Such  flows  are  called  malpais  (bad  country). 
A  large  malpais  near  (S.  of)  the  City  of  Mexico  was   formerly 
the  resort  of  robbers  and  outlaws,  who,  knowing  their  way  over 
it,  found  refuge  from  pursuit  in   its  caverns.     In  what  part  of 
Mexico  is  this  malpais  ?    (See  Plate  41.)] 

9.  1.  About  how  far  W.  of  its  course  in  17 1  is  river  V  in  18  4  ? 
2.  Was  the  displacement  made  all  at  once  ?    In  how  many  partial 
displacements  ?    (Examine  17  2,  18  3,  and  18  4.)    3.    Draw  a  [red] 
line  in  is  4  along  the  divide  (as  far  as  you  can  see  it)  between 
river  Y'  and  the  other  rivers.    4.  Compare  in  17  2,  18  3,  and  18  4  the 
volume  of  river  Y' ;  of  river  V;  explain  the  changes.    5.  Where 
do  rivers   V  and  Z  now  (probably)  unite?    6.  How  much  wider 
than  now  was  the  large  SW.  lava  flow  when  it  was  poured  out  ? 
Explain.    [7.  Draw  in  is  13  a  cross  section  of  valley  V,  18  4,  at  LL'; 


72  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

of  valley  Z  at  MM'.  Why  are  these  two  valleys  not  of  the  same 
shape  ?  8.  Indicate  (dotted  lines.)  in  sections  LL'  and  MM'  the 
original  upland  surface  and  the  original  border  of  the  lava  flows. 
9.  What  relation  exists  between  the  original  border  of  the  lava 
flows  and  the  present  river  courses  ?  10.  Draw  in  15 14  a  cross 
section  from  N  to  N',  18  4,  showing  the  original  upland  and  valley 
profile,  and  the  pipes,  cones,  and  flows  that  are  crossed  by  the  sec- 
tion. 11.  Which  lava  flows  of  18  3  and  18  4  are  shown  in  this  NN' 
section  ?  How  many  volcanic  pipes  are  shown  ?] 

10.  Turn  to  Plate  20.  (Plate  19  is  passed  by  for  the  present.) 
1.  Does  20  5  show  any  signs  of  volcanic  action  later  than  the  latest 
lava  flow  of  18  4  ?  2.  What  changes  has  the  great  volcano  suffered  ? 
Why  may  it  be  called  a  dissected  volcano  ?  3.  Why  do  its  valleys 
radiate  from  its  center  ?  How  many  such  valleys  do  you  think 
there  are  in  the  larger  volcano  ?  in  the  smaller  volcano  ?  4.  To 
what  class  do  these  valleys  belong  ?  [5.  How  many  feet  has  the 
height  of  each  volcano  been  decreased  ?  (Lay  a  piece  of  tracing 
paper,  about  6x7  inches,  on  18  3  ;  mark  the  SE.  and  S  W.  corners 
of  the  block  base  and  the  summit  of  the  W.  volcano ;  lay  the  trac- 
ing paper  in  the  same  position  on  18  4,  and  mark  the  summit  of  the 
great  (E.)  volcano.  Lay  the  paper  in  the  same  way  on  20  5,  and 
mark  the  summit  of  each  volcano ;  measure  decrease  of  height  by 
vertical  scale  on  SW.  block  corner.)  6.  How  many  feet  has  the 
upland,  not  covered  by  lava,  as  at  the  SE.  corner  of  the  block,  20  5, 
been  worn  down  ?  (Use  the  same  tracing  paper  and  trace  the 
front  profile  of  upland  near  SE.  corner  from  n  1  and  2,  18  3  and  4, 
and  20  5.)  7.  Why  has  the  upland  not  been  worn  down  so  much 
as  the  volcanoes  ?  8.  How  many  feet  has  river  V  cut  down  its 
present  valley  near  the  SW.  corner  of  the  district  ?  (Trace  front 
profiles  of  valley,  from  18  3  and  4  and  20  5.)  9.  How  much  has  the 
general  surface  of  the  large  lava  flows  been  worn  down  since  their 
eruption  ?  (Compare  front  border  sections  of  SW.  flow  in  18  4  and 
20  5.)  10.  Compare  the  amount  of  erosion  of  volcano  summits,  gen- 
eral upland  surface,  general  lava-flow  surface,  and  river  valley  F.] 


VOLCANOES  AND  LAVA  FLOWS  73 

11.  1.  About  how  many  feet  has  the  (uppermost)  SW.  lava  flow 
in  20  5  been  narrowed  ?    2.  Has  it  lost  more  on  the  W.  or  on  the  E. 
side  ?    Why  ?    3.  Why  has  erosion  been  greater  (more  rapid)  on  the 
W.  side  than  on  the  general  surface  of  the  flow?    4.  Name  some 
other  parts  of  20  5  where  similar  changes  have  taken  place.    5.  If 
you  ascended  from  river  V,  first  to  the  upland  on  the  W.,  then  to 
the  lava  flow  on  the  E.,  what  difference  would  you  find  in  the  rock 
waste  on  the  valley  sides  ?    6.  Where  would  corresponding  kinds 
of  rock  waste  be  found  in  valley  Z  ?    7.  How  can  the  term  talus 
be  used  here  ?    8.  Why  do  the  streams  of  two  southwestern  val- 
leys of  the  great  volcano  unite  before  reaching  river  Z  ?    9.  Why 
is  the  gorge  of  the  united  stream  narrower  than  the  valley  of  Z? 

10.  In  what  other  part  of  20 5  is  a  similar  gorge  shown?    Why? 

11.  About  how  many  feet  has  the  valley  on  the  N.  side  of  the 
smaller  volcano  been  deepened  ?    12.  Why  do  the  streams  on  the 
N.  and  S.  sides  of  this  volcano  unite  before  reaching  river  UV? 
(Examine  184.)     13.  Why  are  there  no  lakes  in  20  5?     14.  Draw 
a  line  in  20 5  across  valley  UV  from  Q  to  Q';  across  valley  Z  from 
R  to  R'.    [15.  Draw  sections  in  15  13  corresponding  to  the  profiles 
QQ',  RR',  20  5.]    16.  Name,  describe,  explain,  and  indicate  by  appro- 
priate letters  the  features  shown  in  is  16  (scale,  about  1 : 62,500), 
which  resemble  certain  features  of  20  5.    [17.  Complete  the  contours 
in  the  NE.  part  of  15  16.] 

12.  [1.  A  large  volcano  on  Tahiti,  one  of  the  Society  islands  in  the 
S.  Pacific  ocean,  has  been  so  greatly  dissected  that  it  is  now  hardly 
more  than  a  skeleton  of  radiating  ridges.    (See  Dana,  Revised  Text- 
book of  Geology,  p.  130 ;  or  Manual  of  Geology,  fourth  edition,  p.  180.) 
2.  The  Cantal  is  a  deeply  dissected  volcano  in  France ;  it  is  esti- 
mated to  have  lost  about  a  mile  of  its  original  height.    A  road  and 
a  railroad,  following  up  one  valley,  tunneling  through  a  ridge  and 
then  following  down  another  valley,  pass  almost  through  the  center 
of  the  volcano.   3.  In  what  part  of  France  is  the  Cantal  ?   (See  Plate 
43.)  4.  Enormous  lava  flows  form  extensive  plains  in  Idaho,  Oregon, 
and  Washington.    5.  What  parts  of  each  state  does  the  lava  cover  ? 


74  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

(DE,  Fig.  114 ;  DP,  Fig.  130.)  6.  The  level  borders  of  the  most 
recent  flows  contour  around  the  inclosing  mountains,  as  the  ocean 
contours  around  the  continents ;  ridges  stand  forth  in  the  lava 
plain  like  promontories ;  the  lava  plain  enters  valleys  between  the 
promontories,  forming  "  bays  ";  outlying  mountains  rise  like  islands 
over  the  plain  ;  deep  canyons,  cut  by  Snake  river  and  its  branches, 
disclose  lower  mountains  buried  under  the  heavy  lava  sheets. 
(DE,  228.9 ;  DP,  211.4 ;  G,  213.8  ;  T,  125.9 ;  see  also  I.  C.  Rus- 
sell, Water-supply  paper,  No.  4,  U.  8.  G.  S.,  especially  pp.  36,  38, 
34 ;  also,  by  same  author,  Bulls.  199,  217,  252,  U.  S.  G.  S. ;  many 
excellent  plates  ;  also,  by  same  a,uihori  Volcanoes  of  North  America.') 
1.  Smaller  lava  flows  form  a  plateau  (the  Mesa  de  Maya)  in  Colo- 
rado. In  what  part  of  the  state  are  these  flows  ?  (See  Plate  40.) 
In  what  stage  of  dissection  is  this  lava  plateau  ?  (See  36  2  and  3.)] 
13.  1.  The  variable  succession  of  events  in  a  volcanic  district 
may  be  illustrated  as  follows  :  Instead  of  passing  from  18  4  to  20  5, 
let  15  17  follow  18  4.  2.  What  appears  to  have  happened  to  the  great 
volcano  of  18  4  in  15  17  ?  3.  The  large  cavity  in  the  cone  is  called 
a  caldera;  compare  the  caldera  of  15  17  with  the  crater  of  the  great 
volcano  in  18  4,  as  to  diameter ;  as  to  depth.  [4.  Can  the  caldera 
have  been  formed,  like  a  valley,  by  ordinary  stream  erosion?  Ex- 
plain. 5.  Do  the  lava  flows  appear  to  be  covered  with  the  products 
of  an  explosive  eruption,  or  do  they  remain  as  they  were  in  18  4  ? 
6.  How  can  such  a  caldera  be  best  explained  ?  (DE,  221.2;  DP, 
218.8;  G,  217.6;  T,  122.1.)  7.  Compare  184,  1517,  and  20  5  as  to 
opportunity  of  examining  the  internal  structure  of  a  volcano.]  8.  If 
eruptions  begin  again,  a  new  cone  and  new  flows  may  be  formed, 
burying  earlier  forms.  Describe  15  18  as  to  the  forms  there  shown ; 
as  to  the  succession  of  events  there  indicated.  9.  If  an  outflow  of 
lava  occurs  after  a  cone  of  "  ashes  "  has  been  built,  a  great  cavity,  or 
breach,  may  be  opened  in  the  side  of  the  cone  ;  if  the  cone  is  enlarged 
by  eruptions  of  ashes  after  the  flows  have  ceased,  the  form  of  the 
cone  is  more  regular.  10.  Compare  the  cones  of  17  2, 18  3  and  4,  and 
15  18  in  these  respects.  11.  Which  of  the  lava  flows  in  these  figures 


VOLCANOES   AND  LAVA    FLOWS  75 

appears  roughest  ?  [12.  An  extremely  ragged  lava  flow  breaches 
the  N.  side  of  the  cone  of  Jorullo.  13.  "  Crater  lake  "  occupies  a 
great  caldera  in  a  broken-down  volcano  in  Oregon,  mapped  in  38  2. 
(DE,  222;  DP,  215.9-;  G,  217.6;  T,  121.8.  See  J.  S.  Diller,  Nat. 
Geoff  r.  Mag.,  VIII  (1897),  33-48.)  14.  In  what  part  of  Oregon  is 
Crater  lake  ?  (See  Plate  40.)  How  far  N.  of  Mt.  Shasta  ?  15.  What 
are  the  dimensions  of  this  caldera  ?  How  is  its  origin  best  ex- 
plained ?  16.  What  reasons  can  you  give  for  describing  Vesuvius 
(locate  on  Plate  43)  as  "  a  large  cone  built  over  the  western  rim  of 
a  great  caldera "  ?  (DE,  221.8 ;  DP,  213.3 ;  T,  117.3.)  What  is 
the  name  of  the  E.  rim  of  this  caldera  ?  17.  If  a  breached  caldera 
stood  in  the  ocean,  describe  the  shape  of  the  island  that  it  would 
form  ?  18.  Name  and  locate  such  an  island.  (DE,  221.5 ;  DP, 
213.2;  in  S.  Shetland  islands,  Plate  42.)  What  is  its  diameter?] 

14.  1.  Why  have  some  dissected  volcanoes  a  central  peak  or  neck, 
as  in  20  6  ?  2.  Examine  the  side  slopes  of  the  spurs  of  this  great 
volcano,  and  note  a  difference  of  shading  above  and  below  a  certain 
level.  Draw  a  [pencil]  line  along  this  level  on  several  spur  sides ; 
the  altitude  of  this  line  is  about  3100'.  3.  What  is  thus  indicated  as 
to  the  depth  now  reached  in  the  dissection  of  the  volcano  ?  (Exam- 
ine 17  1  and  18  3  as  to  altitude  of  the  central  uplands.)  [4.  How 
much  loss  of  altitude  has  taken  place  on  the  central  summit  of  the 
great  volcano  in  the  change  from  20  5  to  20  6  (use  the  same  trac- 
ing paper  as  in  §  10)?  on  the  even  surface  of  the  SE.  upland  ?  on 
the  general  surface  of  the  SW.  lava  flow  (away  from  streams)?  on 
the  valley  floor  of  river  Z?  of  river  V  ?  5.  Why  has  valley  V  not 
been  as  much  deepened  by  its  large  river  as  the  volcano  summit 
has  been  lowered  by  weather  and  small  streams?]  [6.  Why  does 
a  row  of  sharp  knobs  occur  on  the  SW.  spur  of  the  great  volcano, 
20  6  ?  (See  note  following  question  7,  §  8.)  Where  do  similar  knobs 
occur  ?  Why?  7.  Draw  in  15  15  a  section  crossing  the  SW.,  SSW., 
and  S.  spurs  of  the  great  dissected  volcano  of  20  6,  and  show  the 
features  referred  to  in  question  6.  8.  Why  has  the  middle  spur  a 
different  cross  profile  from  the  other  two  ?] 


76  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

15.  1.  Why  are  the  borders  of  the  lava  flows  in  20  6  more  irregu- 
lar or  "  ragged  "  than  20  5  ?    2.  Has  the  change  of  form  occurred 
chiefly  on  their  upper  surface  or  around  their  borders  ?     Why  ? 
3.  Why  are  the  borders  marked  by  a  vertical  cliff  above  a  steep, 
talus-covered  slope  ?    4.  How  can  the  term  retreat  be  used  in  con- 
nection with  the  changes  of  the  bordering  cliffs  ?    5.  How  can  the 
term  sapping  or  undermining  be  used  in  connection  with  the  retreat 
of  the  cliffs  ?    6.  Which  is  the  more  resistant,  the  country  rock  of  the 
district  or  the  lava  of  the  flows  ?    7.  Why  do  the  lava  flows  now 
form  table  mountains?    8.  Explain  the  relation  of  the  several  table 
mountains  of  20  6  to  the  valleys  of  17  2  and  to  the  lava  flows  of 
184.    9.  Where  are  the  river  gravels  of  the  original  valley  UV, 
17  1,  now  preserved  ?    10.  Suppose  that  the  gravels  contained  grains 
of  gold,  how  could  the  gravels  be  best  mined?    [11.  What  is  the 
origin  of  the  small  knobs  E.  of  valley  V  near  the  SW.  corner  of 
20  6  ?    12.  In  15  13  redraw  sections  QQ'  and  RR'  so  as  to  make  them 
correspond  with  206  instead  of  with  20  5.    (The  proper  depth  of 
valleys  V  and  Z,  20  6,  is  indicated  in  15  13  by  dots  below  sections 
QQ,'  and   RR'.)     Draw  in  15 16  the   outline  of   the   middle  table 
mountain  when  its  length,  NE.-SW.,  is  reduced  by  half ;  of  the  E. 
table  mountain  when  it  is  reduced  to  a  butte.] 

16.  [1.  Many  volcanic  knobs  or  necks  occur  near  Mt.  Taylor,  a 
deeply  dissected  volcano  in  New  Mexico.    (See  article  by  Button, 
6th  Ann.  Rep.,  U.S.G.S.,  p.  164.)    Locate  Mt.  Taylor  on  Plate  40. 

2.  Is  volcanic  action  in  that  district  recent  or  ancient  ?     Why  ? 

3.  A  fine  table  mountain,  called  Raton  mesa  (pron.  may-sa;  Spanish 
for  "table"),  surmounts  the  plains  adjoining  the  Rocky  mountains, 
W.  of  Mesa  de  Maya  in  Colorado ;  part  of  it  is  mapped  in  38  3  ; 
locate  it  on  Plate  40.    4.  What  is  the  scale  of  38  3  ?   The  contour 
interval  is  250'.    The  altitude  of  the  mesa  is  9250';  of  the  plains  on 
the  north  (beyond  the  map),  5500'.   5.  Number  the  contour  lines.  By 
how  many  feet  have  the  plains  been  worn  down  since  the  lava  flow 
of  the  mesa  was  erupted  ?    6.  In  the  Sierra  Nevada,  California,  gold 
is  found  in  gravel  deposits  under  the  lava  cap  of  Table  mountain  ; 


VOLCANOES  AND  LAVA  FLOWS  77 

the  narrow  valleys  on  each   side  of  Table   mountain  are   much 
lower  than  the  gravel  deposits.    (See  Placerville  folio,  U.  S.  G.  S.) 

1.  Draw  a  cross  section  to  illustrate  these  features.     [8.    In  what 
stage  of  the  history  of  the  Sierra  Nevada  (see  Exercise  V,  §  5)  was 
the  lava  flow  of  Table  mountain  erupted?]     9.  A  number  of  ex- 
traordinary wall-like  dike  ridges  occur  near  the  lower  slopes  of  the 
greatly  dissected  volcano,  Spanish  peaks  (about  100  mi.  S.  of  Pikes 
peak),  Colorado;  locate  this  volcano  on  Plate 40.    10.  What  do  the 
dike  ridges  indicate  as  to  the  stage  of  erosion  of  this  volcano  ? 
(See  Spanish  peaks  folio,  U.  S.  G.  £)] 

17.  Now  turn  back  to  Plate  19.    1.  Which  lava  flow  of  18  4  has 
been  completely  worn  away  in  19  7  ?    What  was  its  form  in  20  6  ? 

2.  Compare  the  N  W.  (lava  flow)  table  mountain  in  20  6  and  19  7. 
Has  it  changed  chiefly  in  height  or  in  area?    Why?    3.  By  what 
forms   is   the   NE.  table   mountain   of  20  6  represented  in  19  7  ? 
Explain  the  change.    4.  In  what  part  of  the  SW.  table  mountain 
has   a  similar   change   occurred  ?      5.  How   can  the  terms   head- 
ward  erosion  or  retrogressive  erosion  be  used  in  this  connection  ? 
6.  Why  has  the  retreat  of  the  lava  cliffs  by  sapping  been  greater 
than  the  deepening  of  the  valleys  by  river  erosion,  in  the  change 
from  20  6  to  19  7  ?    7.  In  a  still  later  stage  of  erosion,  which  of  the 
volcanic  features  of  19  7  would  disappear  ?  which  would  remain  ? 
Explain.    [8.  About  how  many  square  miles  of  surface  are  covered 
with  lava  flows  in  18  4  ?  in  19  7  ?   (Draw  on  the  tracing  paper,  already 
used  and  placed  as  before,  a  series  of  lines  parallel  to  the  S.  base- 
line, through  the  half-mile  points  on  the  W.  baseline  ;  another  series 
parallel  to  the  W.  baseline,  through  the  half-mile  points  on  the  S. 
baseline.    What  is  the  area  of  each   "diamond"  thus  marked? 
Place  the  tracing  paper  on  184  and  197  and  estimate  the  desired 
areas.)    9.  About  what   fraction  of   the  original   lava-flow   areas 
remains  in  19  7  ?] 

18.  1.  In  198,  what  is  the  altitude  of  the  central  neck  of  the 
great  volcano  ?    2.  Estimate  the  altitude  of  the  radiating  ridges 
in  the  E.  center  of  the  district,  and  compare  their  altitude  with 


78  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

that  of  the  corresponding  part  of  the  upland  in  17  1.  3.  How 
completely  has  the  great  volcano  been  worn  away  ?  What  parts 
of  it  remain  ?  Why  might  these  parts  be  spoken  of  as  the 
"  roots  "  ?  4.  How  many  necks  and  dikes  are  shown  ?  To  what 
are  they  related  in  the  earlier  figures  of  this  series  ?  Why  are 
they  better  shown  in  19  8  than  in  20  5  or  20  6  ?  5.  What  forms 
are  now  seen  Avhere  the  table  mountains  of  20  6  and  19  7  stood  ? 
Explain.  6.  Why  may  19  8  be  described  as  a  district  of  "  lost  vol- 
canoes"? [7.  Add  a  profile  to  15  14  showing  the  three  necks  as  they 
appear  in  19  8.]  [8.  Several  large  knobs  or  necks  of  volcanic  rock 
(lava)  occur  in  the  St.  Lawrence  valley ;  one  of  them  gives  name 
to  the  chief  city  of  Canada.  (DP,  217.1.)  Volcanic  necks  are  not 
uncommon  in  S.  Scotland.  No  "  table  mountains  "  occur  in  either 
of  these  districts.  9.  What  supposition  may  be  made  as  to  the 
amount  of  erosion  that  has  taken  place  in  those  districts  ?] 

19.  [1.  Describe  in  a  general  way  the  changes  commonly  made 
by  volcanoes  and  lava  flows  in  forming  lakes ;  in  displacing  rivers 
to  one  side  of  their  former  courses ;  in  turning  part  of  one  river 
across  a  divide  to  another  river  system.  2.  What  effect  may  vol- 
canoes and  lava  flows  have  in  shifting  the  point  of  junction  of  two 
streams  ?  in  replacing  a  single  stream  by  two  nearly  parallel  streams? 
in  originating  groups  of  radiating  streams  ?  3.  What  is  the  length 
of  river  UV  in  17  1  and  in  19  8  ?  (Lay  a  thread  or  a  narrow  strip  of 
paper  along  the  turns  of  the  river  and  measure  its  length.)  4.  Com- 
pare the  fall  of  UV  (feet  per  mile)  in  17  1  and  198,  and  explain 
the  difference.  5.  Use  tracing  paper  as  before,  and  copy  rivers  UV, 
Z,  YY'  from  17 1.  6.  Lay  the  tracing  paper  on  19  8.  Why  is  the 
displacement  of  river  UV  in  198  least  near  the  N.  border  of  the 
district  ?  Why  has  it  been  displaced  westward  ?  About  how  far 
has  it  been  displaced  in  its  middle  course  ?  7.  Why  does  a  stream 
run  W.  across  former  mid-courSe  of  UV?  Why  do  the  next  down- 
stream branches  of  UV  (on  E.  side)  run  away  from  the  original 
course  of  UV?  8.  Why  does  the  K  part  of  river  YY',  17  1,  flow 
to  river  U V  in  19  8  ?  Why  is  the  original  lower  part  of  YY'  now 


VOLCANOES  AND  LAVA  FLOWS  79 

represented  by  two  streams  ?    9.  Why  is  river  Z  more  crooked  in 
198  than  in  17  1  ?] 

20.  [1.  A  line  about  9"  long  is  drawn  on  the  side  of  Plate  19. 
Let  this  line  represent  a  very  long  period  of  time.    (The  line  may  be 
imagined  as  extending  indefinitely  in  each  direction,  thus  represent- 
ing earlier  time  without  beginning,  and  later  time  without  end.) 
2.  Turn  the  Atlas  so  that  the  line  is  horizontal.    Mark  small  crosses 
on  the  line  at  0,  £,  1,  and  3  inches  from  its  left  end ;  number  these 
crosses  1 ,  3,  4,  6,  and  let  them  represent  the  dates  of  17  1,  18  3,  18  4, 
and  20  6  in  the  series  of  volcanic  figures  here  studied.    3.  Indicate 
by  other  crosses,  properly  placed  and  numbered,  the  dates  of  17  2, 
20  5,  19  7,  and  19  8.    4.  Print  F,  to  show  the  estimated  date  of  the 
first  volcanic  eruption  ;   L,  to  show  the  last  eruption.     5.  How  far 
to  the  left  of  the  first  cross  would  you  place  a  mark  A,  to  indicate 
the  date  of  the  general  uplift  of  the  region,  as  a  result  of  which 
the  mature  valleys  of  17  1  were  eroded  ?    (Note  that  the  valley  SE. 
of  the  lava  flows  in  20  5  has  a  narrower  floor  than  the  corresponding 
valley  in  17  1.)    6.  How  far  to  the  right  of  cross  8  would  you  place 
another  cross  Z,  to  represent  so  late  a  stage  in  the  cycle  of  erosion 
that  the  hills  of  19  8  shall  have  been  worn  down  almost  flat,  that  is, 
to  a  peneplain  ?     (Erosion  proceeds  more  and  more  slowly  as  hill 
slopes  are  worn  to  less  and  less  declivity.)    7.  During  what  part  of 
the  cycle  AZ  did  the  volcanic  eruptions  FL  occur  ?  8.  Through  (about) 
what  fraction  of  the  cycle  did  the  lava  flows  (table   mountains) 
endure  ?    9.  If  the  whole  cycle  were  something  like  10,000,000  or 
30,000,000  years  long,  how  many  years  were  required  for  building 
the  volcanoes  ?  for  wearing  away  the  lava  flows  ?    10.  Has  the  du- 
ration of  the  cycle  of  erosion  been  lengthened  or  shortened  by  the 
occurrence  of  volcanic  action  ?  11.  Why  may  the  volcanic  phenomena 
be  referred  to  as  "  accidents  in  the  normal  cycle  of  erosion  "  ?] 

21.  Define :    §  2,  volcano,  crater,  lava  flow ;   §  3,  volcanic  lake, 
gorge,  pipe ;    §  4,  volcanic  cinders,  ashes,  and  dust ;   §  6,  volcanic 
pipe  and  neck ;  §  8,  dike,  [malpais]  ;  §  13,  caldera,  breached  vol- 
cano or  cone ;  §  15,  table  mountain ;  §  16,  mesa,  dike  ridge. 


EXERCISE  VII.     THE  RIVER  CYCLE :  WATERFALLS, 
RAPIDS,   AND   GRADED  RIVERS 

OBJECT.  To  study  various  problems  in  connection  with  the  devel- 
opment of  rivers. 

Preliminary.  21 1  is  a  block  diagram  of  part  of  a  lowland 
crossed  by  a  number  of  low  E.-W.  ridges  and  drained  by  two  S.- 
flowing  rivers,  R  and  Q.  The  lowland  is  so  nearly  level  that  much 
of  the  rainfall  sinks  into  the  soil  or  dries  off  from  the  surface; 
hence  the  number  of  branch  streams  is  small.  Each  block  is  about 
4  mi.  wide.  A  scale  of  miles  is  marked  along  the  W.  baseline  of 
the  block.  The  shore  of  the  ocean  is  shown  near  the  S.  end  of  the 
block.  The  dotted  line  on  the  W.  block  face  indicates  sea  level ; 
the  short  vertical  lines  rising  from  it  show  altitudes  of  100'.  (The 
vertical  scale  is  much  exaggerated.)  The  following  figures,  21  2,  22  3 
and  4,  etc.,  illustrate  later  stages  in  the  history  of  the  same  district 
as  21 1,  as  it  is  uplifted  and  dissected.  This  exercise  uses  21,  22,  23, 

24,  26,  1-12. 

1.  1.  What  is  (about)  the  altitude  of  the  lowland  at  the  N.  end 
of  21 1  ?  What  is  the  fall  of  river  R  per  mile  ?  2.  About  how  high 
are  the  ridges  over  the  lowland  ?  3.  The  lowland  has  a  fine  deep 
soil ;  the  low  ridges  have  a  thin  stony  soil.  What  can  you  infer  as 
to  the  resistance  of  the  rocks  under  the  low  ridges,  as  compared  to 
that  of  the  rocks  under  the  lowland?  4.  In  what  stage  of  a  cycle 
of  erosion  does  this  district  seem  to  be  ?  [5.  Draw  a  IST.-S.  pro- 
file in  21 1  b  across  belts  E,  D,  C,  along  the  middle  N.-S.  line  of 
21 1.  6.  Draw  an  E.-W.  profile  in  21 2  b  along  belt  E.]  7.  21 2 
shows  a  later  stage  in  the  history  of  the  district.  (Altitudes  of  0', 
200',  400',  and  600'  are  shown  by  dotted  lines,  and  the  profile  of  21 1 
is  drawn  in  a  broken  line  on  the  W.  block  face  of  21  2.)  8.  Compare 

80 


THE  RIVER  CYCLE  81 

the  altitudes  of  21 1  and  21  2  in  the  NE.  corner ;  NW.  corner ;  at 
W.  and  E.  ends  of  belt  L ;  of  belt  H ;  of  belt  E ;  along  the  shore 
line  of  21 1.  9.  Has  the  district  been  evenly  or  unevenly  uplifted  ? 
10.  Why  do  lakes  S  and  T  occur  ?  NOTE  :  It  is  not  usual  to  find 
lakes  produced  by  uneven  uplift  or  warping  of  the  earth's  crust, 
because  the  basins  thus  formed  are  usually  filled  with  inwashed 
waste  (as  well  as  cut  down  at  the  point  of  river  overflow)  while 
the  warping  goes  on.  11.  What  may  be  inferred  from  this  as  to 
the  rate  at  which  warping  usually  takes  place  ?  [12.  What  other 
illustration  of  the  rate  of  crustal  warping  have  you  had  in  these 
exercises  ?] 

2.  1.  Where  has  the  waste  from  the  head  waters  of  rivers  R  and 
Q,  21 2,  been  deposited?    2.  Why  may  lakes  be  regarded  as  "river 
filters"?    3.  Mark  [blue]  the  shore  line  that  lake  T  would  have  had 
if  the  head  streams  of  Q  had  not  formed  a  delta  in  it.    4.  About 
how  much  has  the  outlet  of  lake   T  been  cut  down  in  ridge  J? 
5.  Draw  a  broken  [blue]  line  to  show  the  shore  line  that  you  think 
lake  T  would  have  had  if  its  outlet  had  not  been  cut  down  by  stream 
Q  in  ridge  ,/.    6.  Why  is  the  delta  in  lake  S  larger  than  the  delta 
in  lake  T  ?     7.  If  -R  had  been  a  much  larger  river  than  it  is,  what 
effect  might  it  have  had  on  the  occurrence  of  a  lake  in  basin  S  ? 
[8.  Compare  the  altitudes  of  the  W.  part  of  ridge  J,  lake  S,  and 
the   land   between   lakes    S   and    T.     9.  Where  would   the  outlet 
(overflow)  of  lake  S  be,  if  river  R  had  not  been  able  to  cut  a  notch 
in  ridge  /  during  the  warping  of  the  district  ?    10.  Compare  the 
direction  of  general  land  slope  in  21 1  with  the  direction  of  land 
slope  from  ridge   /  to  lake  S  in  21  2.    11.  Why  was  river  R  not 
turned  eastward  to  lake  T  while  this  local  northward  slope  was 
upwarped  across  its  course  ?    12.  What  name  is  given  to  rivers  of 
this  class  ?    (Exercise  V,  §  9.)     13.  In  what  part  of  their  courses 
are  rivers  R  and  Q  antecedent  ?] 

3.  1.  Determine  the  average  fall  in  21  2  of  river  R   from  the 
notch  in  ridge  J  (altitude,  400')  to  the  sea,  and  compare  it  with  the 
average  fall  of  .R  in  21 1.     2.  What  effect  has  the  increase  of  fall  had 


82  EXERCISES  IN   PHYSICAL  GEOGRAPHY 

on  the  behavior  of  the  river  ?  3.  What  term  may  be  applied  to  rivers 
whose  activity  is  thus  increased  ?  (Exercise  V,  §  5.)  4.  How  many 
waterfalls  occur  on  R  in  21  2  ?  5.  Does  the  location  of  the  four 
larger  falls  on  R  confirm  the  inference  already  made  (§  1,  ques- 
tion 3)  as  to  the  occurrence  of  resistant  rocks  under  the  low  ridges 
of  21 1  ?  Explain.  6.  How  are  the  waterfalls  related  to  the  resist- 
ant and  weak  rocks?  (DE,  252.2;  DP,  236.1;  &,  38.8 ;  T,  54.1.) 

7.  How  may  the  six  small  falls  on  river  R,  21  2  (marked  by  short 
lines  across  the  river),  in  the  weaker  rocks  B,  D,  F,  H,  be  accounted 
for  ?     8.  In  what  parts  of  a  district  like  21  2  would  you  look  to  find 
the  attitude  (horizontal,  slanting  upstream  or  downstream,  vertical) 
of  the  rock  layers  ?    9.  What  is  the  attitude  of  the  rock  layers  in 
22  3 c  ?   in  22 4  a?    10.  To  what  parts  of  21  2  might  the  larger-scale 
22  3  c  correspond  ?    [11.  Draw  a  [red]  line  in  22  3  c,  separating  the 
resistant  strata  from  the  weaker  strata.]    NOTE  :  The  steep  walls 
of  a  river  gorge  show  many  rock  outcrops  from  which  the  structure 
of  the  district  may  be  determined.    12.  How  is  the  structure  of  the 
district  here  studied  represented  on  the  W.  block-face  of  the  figures 
in  this  exercise  ?    13.  What  is  the  general  attitude  of  the  groups 
of  strata,  or  formations,  there  represented  ? 

4.  1.  What  determines  the  depth  to  which  the  valley  of  river  R, 
21  2,  has  been  eroded  upstream  from  formation  J?  2.  Why  may 
the  notch  in  each  resistant  formation  be  regarded  as  the  local  base- 
level  with  respect  to  which  the  next  upstream  weaker  formation  is 
worn  down  ?  3.  Why  is  the  valley  of  river  R,  21  2,  deeper  in  forma- 
tion B  than  in  formation  A"  ?  4.  Why  are  the  falls  from  formation 
J  higher  than  from  formation  G?  5.  A  river  flowing  through  a 
narrow  gorge  usually  has  certain  parts  of  even  flow  (reaches'),  cer- 
tain parts  of  hurried,  uneven  flow  (rapids),  and  certain  parts  of 
steep  or  vertical  plunge  (falls').  6.  Mark  in  22  3  c  and  22  4  a  a  full 
[blue]  line  on  the  reaches,  a  broken  [blue]  line  on  the  rapids,  and 
a  dotted  [blue]  line  on  the  falls.  7.  How  are  reaches,  rapids,  and 
falls  related  to  the  occurrence  of  resistant  and  weak  formations  ? 

8.  How  many  reaches  separated  by  how  many  falls  occur  on  river 


THE   RIVER   CYCLE  83 

R,  21  2  ?  (The  rapids  in  the  notches  are  too  small  to  be  shown  in 
this  figure  ;  they  are  indicated  in  22  3  c.)  [9.  Draw  in  21 1  c  a  N.-S. 
profile  across  belts  E,  D,  f,  as  they  are  seen  on  the  W.  border  of 
21  2  ;  and  in  21 1  d,  a  profile  across  the  same  belts  along  river  R,  21  2. 

10.  Indicate   the  underground   structure   beneath   these    profiles. 

11.  Draw  in  21  2  c  an  E.-W.  profile  along  belt  E,  21  2  ;  and  in  21  2d, 
an  E.-W.   profile  along   belt  />;    add  lines  to  the  last  profile  to 
represent  the  side  streams  in  belt  />.] 

5.  NOTK  :  22  3  shows  a  greater  amount  of  up-warping  than  21  2. 
(The  profiles  of  21 1  and  21  2  are  marked  in  broken  lines  on  the  W. 
block-face  of  223.)    1.  About  how  much  uplift  has  occurred  from 
21  2  to  22  3  in  the  1ST.  part  of  the  district  ?    in  the  center  ?    in  the 
southern  part  ?    2.  What  has  happened  in  22  3  to  lakes  S  and  T  of 
21  2  ?    3.  Describe  the  course  of  river  R  as  to  reaches,  rapids,  and 
falls    in    22  3.     4.  Where  has   a  new  fall  been   formed  ?     Why  ? 

5.  Where  have  some  small  falls  been  destroyed  ?    How  and  why  ? 

6.  How  are  the  reaches,  formerly  separated  by  the  small  falls,  now 
related  ?    7.  Compare  the  height  of  the  falls  from  C  and  E  (the 
C  and  E  falls)  in  21  2  and  22  3.    8.  Why  have  the  falls  decreased 
in  height  at  one  place,  and  increased  at  the  other  ?     [9.  Answer 
similar  questions  for  the  G  and  J  falls.]    10.  Why  is  the  valley  of 
/.'  deeper  in  formation  B  than  in  formation  M?    in  D  than  in  F  ? 
in  //  than  in  F  ?    11.  Why  is  the  valley  of  Q  in  general  less  deep 
than  the  valley  of  R  ?    [12.  Draw  E.-W.  profiles  in  22  3  ab  on  belts 
./  and  //,  22  3.] 

6.  1.  Compare  the  altitudes  of  E,  J,  and  L  on  the  W.  profile  of  22  3 
and  22  4.    2.  Has  22  4  been  uplifted  as  compared  with  22  3  ?   3.  What 
general  change  has  taken  place  in  the  depth  of  the  R  and  Q  valleys  ? 
in  their  width  ?    4.  Has  the  number  of  falls  on  R  changed  ?    Ex- 
plain.   5.  Has  the  number  of  reaches  changed  ?    Explain.    6.  The 
uppermost  line  of  26  9  shows  the  profile  of  the  W.  border  of  the  up- 
land of  22  3.     (The  vertical  scale  is  here  exaggerated  over  the  hori- 
zontal about  16  times.)    The  line  in  269  marked  3,  3,  3  shows 
part  of  the  profile  of  river  R  for  22  3.    7.  Complete  the  profile  in 


84  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

formations  D  and  B.  8.  Several  short  lines  marked  4  indicate  parts 
of  the  profile  of  R  in  22  4.  Complete  this  profile.  9.  Compare 
the  number  of  falls  and  reaches  in  22  4  (or  profile  4)  and  in  21  2. 
10.  What  change  has  taken  place  in  the  number  of  falls  ?  in  the 
number  and  length  of  the  reaches  ?  Explain.  11.  What  would 
you  expect  as  to  the  number  and  length  of  separate  reaches  at 
an  earlier  stage  of  gorge  erosion  than  21  2  ?  at  a  later  stage  than 
22  4  ?  Explain.  12.  On  what  sort  of  strata  are  the  falls  earliest 
worn  down  ?  latest  worn  down  ?  13.  On  what  sort  of  strata  are 
uninterrupted  reaches  soonest  developed  ?  14.  How  may  the  term 
grade  be  used  in  this  connection?  (See  Exercise  III,  §  4  ;  DE,  254.4; 
DP,  237.5  ;  T,  5G.8.)  [NOTE  :  Several  streams  in  NE.  Pennsylvania 
flow  across  an  inclined  series  of  strong  and  weak  formations. 
Waterfalls  occur  where  the  streams  pass  from  the  strong  to  the 
weak  formations.  15.  Which  figure  in  Plate  22  gives  best  illus- 
tration of  these  falls?  16.  Explain  their  origin.  17.  Where  do 
graded  reaches  probably  occur  on  these  streams  ?] 

7.  1.  Draw  in  26  9,  through  the  lines  marked  5,  the  profile  of  R 
for  23  5.  2.  Which  falls  are  now  almost  reduced  to  rapids  ?  Why  ? 
3.  Draw  profile  6  in  26  9.  4.  Why  have  the  E  falls  decreased  in 
height  ?  5.  Why  are  the  C  and  G  rapids  almost  obliterated  ? 

6.  Compare  the  amount  of  erosion  on  C  and  L  between  profiles  5 
and  6.    Which  has  been  eroded  by  the  greater  amount  ?    Why  ? 

7.  Why  have  the  C  falls  been  decreased  and  the  L  falls  been  in- 
creased in  height  during  this  interval  ?    8.  Draw  profiles  7  and  8 
in  26  9.    9.  Compare  profiles  3  and  8  as  to  number  of  falls  ;  height 
of  falls;  number  and  length  of  reaches.    10.  Why  are  the  /rapids 
longer  but  less  steep  in  profile  8  than  in  profile  3  ?    [11.  Examine 
the  upper  profile  of  24  8  a.    Are  the  resistant  formations  odd-num- 
bered or  even-numbered  ?    12.  Complete  the  river  profiles  m,  m 
and  n,  n.    13.  Draw  some  additional  river  profiles.    14.  Which  fall- 
making  formations  will  have  been  worn  downward  (nearly  verti- 
cally) when  their  falls  are  extinguished  (or  obliterated)  ?    Which 
will  have  been   worn  backward  (upstream   nearly  horizontally)  ? 


THE  RIVER  CYCLE  85 

Why  ?  15.  Examine  the  river  profiles  in  24  7  a,  b,  c.  What  is  the 
attitude  of  the  strata  in  each  figure  ?  16.  Print  F  on  each  fall- 
making  formation.  17.  Let  the  lower  broken  line  in  each  figure 
represent  the  profile  that  the  river  will  have  when  it  is  graded 
across  the  fall  maker  (as  in  profile  8,  of  269);  prolong  this  graded 
profile  upstream.  18.  In  which  figure  must  the  fall  maker  be 
eroded  by  the  greatest  amount  before  the  fall  is  obliterated  ? 
by  the  least  amount  ?  Why  ?]  [19.  Several  rivers  flowing  E. 
from  the  highlands  of  the  Transvaal,  S.  Africa  (locate  on  Plate  45), 
have  worn  deep  valleys  across  inclined  strata  (slanting  W.).  To 
what  ocean  do  these  rivers  flow  ?  Elands  river,  in  the  S.  part  of 
Portuguese  East  Africa,  still  has  two  falls  where  it  crosses  the 
most  resistant  formations  of  its  course.  With  which  falls  in  235 
do  these  two  falls  correspond  ?  20.  The  Potomac  river  has  eroded 
a  deep,  narrow  notch  in  the  inclined,  resistant  strata  of  the  Blue 
ridge  at  Harpers  Ferry ;  there  the  river  flows  in  shallow  rapids 
across  the  edges  of  the  rock  layers.  Locate  Harpers  Ferry  in  rela- 
tion to  the  neighboring  states.  (See  Plate  40.)  What  effect  have 
the  rapids  on  the  navigation  of  the  Potomac?  21.  On  what  for- 
mation are  similar  rapids  shown  in  24  7  ?] 

8.  [1.  Compare  the  position  of  the  falls  on  formations  C  and  L 
in  profiles  3,  5,  and  8  of  26  9,  as  to  distance  from  river  mouth.  (Meas- 
ure the  distances  on  the  scale  of  miles  at  base  of  26  9  ;  the  forward 
growth  of  R  delta  in  the  sea  may  be  neglected  in  this  connection.) 
2.  Why  are  the  falls  or  rapids  on  these  formations  farther  from 
the  river  mouth  in  profile  5  than  in  profile  3  ?  3.  Why  has  the 
increase  of  distance  from  river  mouth  in  the  L  falls  been  greater 
than  in  the  C  falls  ?  4.  Why  may  the  L  falls  be  described  as 
having  been  worn  back,  or  as  having  retreated,  while  those  from 
C  have  been  mostly  worn  down  ?  5.  How  far  have  the  L  falls  re- 
treated between  profiles  6  and  8  ?]  [6.  Compare  the  slope  of  the 
graded  reaches  in  profiles  3  and  8  of  26  9.  Explain  the  difference. 
(Consider  in  this  connection  the  amount  of  waste  received  by  the 
river  from  its  valley  sides  and  its  side  streams  in  these  two  stages. 


86  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

Examine  22  3  and  24  8.)  7.  If  the  N.  extension  of  formation  L 
be  horizontal,  how  far  must  its  waterfall  retreat  before  it  is  obliter- 
ated or  extinguished  (the  grade  of  the  river  remaining  as  in  profile 
8  of  26  9)?  8.  Suppose  that,  during  the  retreat  of  the  L  falls,  the 
rapids  on  J  are  worn  down  lower  than  profile  8 ;  what  effect  will 
this  have  on  the  retreat  needed  for  the  obliteration  of  the  L  falls  ? 
9.  Suppose  that,  during  the  retreat  of  the  L  falls  and  the  re- 
duction of  the  ./  rapids,  the  slope  of  the  graded  reaches  in  river 
R  is  lessened  (because  the  load  to  be  carried  is  lessened) ;  what 
effect  will  this  have  on  the  amount  of  retreat  of  the  L  falls  before 
they  are  obliterated  ?  10.  Which  are  longer  lasting,  falls  from 
vertical,  from  inclined,  or  from  horizontal  strata  of  the  same 
resistance  ?] 

9.  [1.  Assume  the  amount  of  water  that  is  discharged  by  river 
R  to  be  the  same  in  all  the  chief  figures  of  this  exercise.  Does  the 
river  flow  faster  in  21 1  or  22  3  ?  2.  Then  in  which  figure,  21  1  or 
22  3,  should  the  river  be  broader  ?  (If  a  slow-flowing  and  a  fast- 
flowing  river  discharge  the  same  amount  of  water,  the  fast-flowing 
river  will  be  narrower  than  the  other.  Explain.)  3.  In  what  part 
of  the  river  in  22  3  would  you  expect  it  to  be  narrowest  ?  broadest  ? 
(See  21  2  a,  22  3  c,  and  22  4  a.)  Why  ?  4.  In  what  part  deepest  ? 
shallowest?  (The  plunge  of  a  large  river  from  high  falls  scours 
out  a  deep  pool  in  the  weak  strata  below  the  falls  ;  the  rush  of 
flood  waters  wears  the  weak  strata  of  graded  reaches  somewhat 
deeper  than  the  hard  strata  of  rapids.)  5.  If  river  R  should  cease 
running  in  a  dry  season,  where  would  pools  remain  in  its  channel  ? 
6.  What  sort  of  a  lake  is  shown  near  the  S.  part  of  river  R  in 
24  8  ?  Compare  it  as  to  origin,  size,  and  stage  of  river  develop- 
ment with  the  two  lakes  of  21  2.  7.  In  which  of  the  chief  figures 
of  the  exercise  would  river  R  be  most  easily  followed  by  boats  or 
rafts  ?  8.  If  an  Indian  came  down  river  .R  of  23  5  in  a  canoe,  how 
many  "  carries "  would  he  have  to  make  ?  (A  carry  or  portage 
must  be  made  where  the  falls  or  rapids  are  so  steep  that  the  canoe 
has  to  be  carried  along  the  river  bank.)] 


THE   RIVER  CYCLE  87 

10.  1.  The  occurrence  of  many  falls  and  rapids  in  the  course 
of  a  river  indicate  that  it  is  in  an  early  stage  of  development ;  the 
river  is  then  young.    As  the  falls  and  rapids  are  obliterated  and 
the  separate  reaches  unite  in  a  long-continuous  graded  course,  the 
river  is  mature.    When  the  valley  floor  has  been  widened  and  the 
graded  course  worn  down  to  a  very  gentle  slope,  the  river  is  old. 
2.  In  which  of  the  chief  figures  of  this  exercise  is  river  R  young  ? 
in  which  one  is  it  mature  ?  old  ?    [3.  Other  indications  of  the  stage 
of  development  of  a  river  are  to  be  found  in  its  velocity,  in  the  quan- 
tity and  texture  of  its  load,  in  the  breadth  of  its  flood  plain,  etc. 
4.  State  some  of  these  indications.]    5.  Through  what  changes  do 
you  think  R  had  passed  before  it  reached  the  condition  shown  in 
21 1  ?    [6.  Let  the  chief  figures  of  this  exercise  illustrate  a  "  cycle  of 
river  development,"  in  which  the  stages  of  21 1,  22  3,  23  6,  and  24  8 
are  indicated  by  corresponding  numbers  over  the  time  line  of  26  10. 

7.  Add  other  numbers  to  show  the  stages  of  21  2,  22  4,  23  5,  and  24  7. 

8.  Print  PERIOD  OF  UPLIFT  under  the  proper  part  of  the  time 
line.    9.  With  what  stage  of  river  development  is  the  period  of 
uplift  associated  ?   Why  ?    10.  Are  the  processes  of  erosion  more 
active  on  the  steep  slopes  of  youth  or  on  the  faint  slopes  of  old 
age  ?    11.   In  view  of  this,  about  how  far  to  the  right  of  stage  8  in 
26  10  should  a  ninth  stage,  with  slopes  and  relief  as  small  as  in 
21 1,  be  placed  ?    12.  Which  is  of  longer  duration,  youth,  maturity, 
or  old  age  of  a  river  ?    13.  What  stage  of  river  development  had 
been  reached  in  the  cycle  during  which  21  1  was  developed,  when  it 
was  interrupted  by  the  warping  uplift  which  introduced  the  cycle 
here  studied  ?] 

11.  Define :    §  3,  formation ;   §  4,  local  baselevel,  reach,  rapids, 
falls ;  §  6,  grade  ;  §  8,  retreating  waterfalls,  worn-down  waterfalls, 
obliterated  waterfalls  ;  [§  9,  portage  or  carry  ;]   §  10,  cycle  of  river 
development,  youth,  maturity,  and  old  age  of  a  river. 


EXEECISE   VIII.      THE   EIVEE   CYCLE:    EIDGES, 
VALLEYS,  AND  EIVER  CAPTUEES 

OBJECT.  To  study  the  origin  of  longitudinal  ridges  and  valleys,  and 
the  rearrangement  of  river  courses  associated  with  these  features. 

Preliminary.  The  figures  used  in  the  previous  exercise  serve  for 
this  exercise  also. 

1.  1.  In  21 2,  why  are  the  notches  cut  by  rivers  R  and  Q  in  the 
harder  formations  C,  E,  etc.,  V-shaped,  instead  of  having  vertical 
walls  ?  2.  Draw  a  [red]  line  along  the  top  of  the  valley  sides  of 
rivers  R  and  Q  in  formations  E,  F,  and  G.  (Neglect  the  E.  and 
W.  side  ravines  for  the  present.)  [3.  21 1  a  is  a  contour  map  of 
belts  E,  F,  G;  complete  the  contours  W.  of  river  R.  4.  21  2 a  is  a 
hachure  map  of  belts  C,  D,  E  ;  complete  the  hachures  W.  of  river 
R.  Mark  a  [red]  line  in  21  2  a  along  the  top  of  the  valley  sides  of 
valleys  R  and  Q.]  5.  In  which  belts  is  valley  R  wider  (at  level  of 
upland)  ?  In  which  belts  is  it  narrower  ?  6.  Why  does  its  width 
vary  ?  7.  Make  a  general  rule,  stating  the  relation  between  the 
width  of  a  young  valley  and  the  resistance  of  the  formations  in 
which  it  is  eroded.  8.  By  how  many  instances  is  this  rule  sup- 
ported in  21  2  ?  9.  If  the  valley  of  river  R  is  wider  in  formation  F 
than  in  formation  E,  why  is  it  not  also  eroded  to  a  lower  level  in 
F  than  in  E  ?  10.  Examine  the  R  valley  in  22  3  and  4  with  regard 
to  the  relation  between  rock  resistance  and  valley  form,  and  then 
complete  the  following  statement :  The  width  of  a  young  valley 
that  is  eroded  across  a  weak  formation  is  independent  of,  and  is 
usually  greater  than,  the  width  of  the  valley  notches  eroded  in 
neighboring  strong  formations ;  but  the  depth  to  which  a  young 
valley  can  be  eroded  across  a  weak  formation  .  .  .  11.  What 
effect  has  the  revival  of  R  and  Q  had  on  their  branch  streams  ? 

88 


THE   RIVER  CYCLE  89 

12.  Do  the  branches  join  the  main  rivers  in  accordant  or  in  hang- 
ing fashion  ?    Why  ? 

2.  1.  In  22  3  draw  a  light  [red]  line  along  the  divide  between  the 
drainage  areas  of  rivers  R  and  Q.    Why  may  the  divide  be  called 
ill  defined?    2.  Compare  the  cross  (E.-W.)  profiles  of  R  valley  in 
formation  J,  21  2  and  22  3.    [Complete  the  profiles  in  21  2  c  and  22  3  a.] 
Do  the  same  for  R  valley  in  formation  H.    [Complete  the  profiles 
in  21  2  d  and  23  3  b.~\    Explain  the  changes.    3.  Complete  in  22  4  b  the 
E.-W.  profiles  on  formations  //  and  J,  22  4.   (See  J4  and  7/4.)    4.  How 
have  they  changed  from  the  corresponding  profiles  for  22  3  (J3  and 
Hs  in  22  4  i)  ?    5.  In  22  4,  how  many  side  streams  join  river  R  from 
the  east  in  formation  //?    How  many  join  river  Q  from  the  east  in 
formation  A'?    6.  Draw  a  light  [red]  line  along  the  divide  between 
the  drainage  areas  of  rivers  R  and  Q  in  22  4 ;  make  the  line  heavier 
on  the  well-defined  parts  of  the  divide  than  on  the  rest.    7.  Why 
are  some  parts  of  the  divide  better  defined  than  others  ?    8.  Why 
are  the  head-water  ravines  of  river  Q  longer  in  22  3  than  in  21  2  ? 
(Use  the  terms  head-ward  erosion  or  retrogressive  erosion  in  answering 
the  preceding  question.)    9.  Why  does  (most  of)  the  divide  between 
the  two  head  branches  of  river  Q  follow  a  sharp-crested,  notched 
(serrate)  ridge,  while  the  divide  between  rivers  Q  and  R  on  forma- 
tion M  lies  on  a  smooth-sloping  upland  ? 

3.  1.  Draw  in  23  5  a  [red]  line  along  the  divide  between  rivers 
R  and  Q.    2.  What  parts  of  the  divide  are  still  ill  defined  ?    Why  ? 
3.  23  5  b  shows  (on  a  somewhat  larger  scale)  unfinished  E.-W.  pro- 
files across  the  divide  on  formation  H  for  several  stages  of  this 
exercise.    Complete  the  profile  for  stage  5.    Is  the  divide  definite  or 
indefinite  ?    4.  Which  part  (E.  or  W.)  of  formation  H  was  most  up- 
lifted in  22  3  ?   5.  Then  why  is  river  R  at  a  lower  level  than  river  Q 
in  stage  5,  23  5  b  ?    6.  Why  is  the  divide  not  halfway  between  R  and 
Q  ?    7.  At  a  stage  of  erosion  between  the  stages  of  23  5  and  23  6  the 
channels  of  rivers  R  and  Q  in  formation  H  are  shown  on  line  5-6  in 
23  5  b.    Why  has  jR  deepened  its  valley  more  than  Q  ?    8.  Complete 
the  E.-W.  profile  for  the  stage  between  stages  5  and  6.    9.  How  has 


90  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

the  divide  (in  23  5  b)  between  R  and  Q  been  changed  as  to  form  ?  as 
to  altitude  ?  10.  How  has  it  been  shifted  with  respect  to  R  and  Q  ? 
11.  Which  river  (R  or  Q}  is  gaining  and  which  is  losing  drainage 
area  in  formation  //?  Why?  12.  Which  side  streams  (of  R  or 
of  Q)  are  most  effective  in  shifting  (by  headward  erosion)  the  posi- 
tion of  the  divide  ?  13.  What  advantage  have  these  side  streams, 
that  makes  them  more  effective  ?  14.  How  does  the  length  of  the 
side  streams  change  as  the  divide  shifts  or  migrates?  15.  Fill  in 
the  blanks  in  the  following  statement :  When  a  smooth  lowland 
is  uplifted  the  .....  divides  between  the rivers  are  gradu- 
ally made by  the erosion  of  the  side  streams  ;  and 

then  as  the divides  are  slowly they  are  also  slowly 

toward  the rivers ;  and  thus  the rivers  slowly 

gain  a  larger  drainage  area.  16.  Mark  a  [blue]  2^1IS  sign  (+)  in 
23  5  at  several  points  where  river  R  has  recently  gained  drainage 
area  by  the  shifting  of  the  R-Q  divide  ;  and  a  [red]  minus  sign  (— ) 
at  points  where  Q  is  losing  drainage  area. 

4.  1.  With  what  part  of  235  does  the  enlarged  sketch  in  26  11 
correspond  ?  2.  What  river  receives  the  drainage  from  surfaces 
b,  b,  2611?  from  surfaces  a,  a?  3.  Draw  a  [red]  line  in  2611 
along  the  divide  between  the  side  branches  of  Q  and  R  (R  is  not 
shown).  4.  What  is  the  general  altitude  of  the  foreground  low- 
land (a)  on  formation  H  ?  of  the  same  formation  near  river  Q  ? 
5.  What  has  caused  this  difference  in  altitude  ?  6.  What  effect  will 
continued  erosion  have  on  the  length  of  streams  hl  and  h2  ?  on  the 
position  of  the  R-Q  divide  ?  7.  Draw  a  broken  [red]  line  to  show 
the  R-Q  divide  at  a  somewhat  later  stage  (when  its  distance  from 
river  Q  is  halved).  8.  Draw  in  23  55  an  E.-W.  profile  for  the  same 
later  stage  (between  stages  5-6  and  6).  9.  If  changes  of  this  kind 
go  on,  what  will  happen  to  river  Q  ?  10.  Draw  a  [blue]  line  in 
26 11  to  show  what  you  expect.  11.  Illustrate  the  same  change  by 
drawing  a  new  profile  in  23  5  b.  12.  Why  may  the  expected  change 
be  described  as  river  capture  or  river  diversion  ?  NOTE  :  As  the 
divide  is  shifted  close  to  river  Q,  more  and  more  of  its  water 


THE   RIVER   CYCLE  91 

will  pass  underground  and  enlarge  the  springs  that  feed  the  head 
waters  of  streams  h1,  2611.  13.  When  the  expected  change  has 
happened,  which  river  may  be  called  captured  or  diverted?  Which 
stream  may  be  called  the  di verier?  14.  Why  may  the  lower  part 
of  river  Q  then  be  described  as  beheaded?  (See  Q',  26  12.)  15.  How 
Avill  the  volume  of  the  beheaded  river  be  affected  ?  16.  To  what 
river  will  the  upper  part  of  river  Q  (see  Q",  26  12)  then  flow  ? 

5.  1.  Draw  a  [red]  line  in  26  12  and  23  6  along  the  divide  between 
rivers  R  and  Q'.  2.  In  what  important  respect  has  the  divide  been 
changed  from  the  divide  in  2611  and  23  5?  3.  Has  the  greatest 
part  of  this  change  taken  place  slowly  or  (relatively)  rapidly? 
4.  If  the  shifting  or  migration  of  the  divide  between  stages  4,  5, 
and  5-6,  in  2:5  5  b,  be  described  as  creeping,  what  part  of  the  shift- 
ing may  be  described  as  leaping  ?  5.  Why  may  the  point  where  the 
capture  was  made  be  called-  the  elbow  of  capture  ?  6.  Print  W  at 
this  point  in  26  12.  7.  Why  lias  river  Q"-hl  deepened  its  valley 
downstream  from  the  elbow  of  capture  ?  and  also  upstream  from 
the  elbow  ?  8.  Why  is  the  valley  of  Q"  in  formation  K  not 
deepened  in  26  12  ?  9.  Which  waterfall  is  higher  as  a  result  of 
this  river  capture  ?  10.  What  has  happened  in  26 12  (since  the 
leaping  of  the  divide  around  the  upper  part  of  river  Q)  as  to 
erosion  along  stream  7/2?  along  streams  h3  and  h*  ?  11.  Explain 
these  happenings.  12.  What  changes  may  be  expected  to  take 
place  (in  the  not  distant  future)  in  stream  h5  ?  in  stream  h6  ? 
13.  What  part  of  these  last  changes  is  made  by  creeping  ?  by  leap- 
ing ?  What  is  the  relative  importance  of  creeping  and  leaping  in 
these  changes  of  the  divide  ?  14.  WThat  change  will  take  place 
at  the  same  time  in  the  volume  of  the  G  waterfall  of  stream  Q'  ? 
in  the  volume  of  h1  ?  15.  Draw  in  26  12  broken  [blue]  lines  to 
show  the  future  courses  of  streams  h5  and  7i6 ;  a  broken  [red]  line 
to  show  the  divide  between  Q"-hl  and  Q',  when  these  changes  have 
gone  on  as  far  as  they  can.  16.  23  5  a  shows  on  a  larger  scale  a 
part  of  river  Q,  on  formation  F  of  23  5.  Compare  the  size  of  the 
stream  curves  with  the  size  of  the  valley  curves.  How  have  the 


92  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

valley  curves  been  produced  ?  17.  23  6  b  shows  the  same  district 
for  23  6.  Compare  the  valley  curves  in  23  5  a  and  6  b ;  the  stream 
curves.  18.  Explain  the '  changes.  19.  Why  may  the  stream  of 
23  6  b  be  described  as  a  misfit  for  its  valley  ? 

6.  1.  At  what  other  points  in  23  6  may  stream  captures  take 
place  in  the  future  ?  2.  How  many  captures  (besides  the  one 
shown  in  23  6)  have  taken  place  during  the  development  of  24  7  ? 

3.  Print  W  at  all  the  "elbows  of  capture  "  that  you  can  find  in  24  7. 

4.  Print  X  at  points  of  capture  where  "  no  elbow "  was  made  (as 
will  be  the  case  with  streams  h5  and  h6,  2612).    5.  Draw  a  [red] 
line  in  247  along  the  divide  between  the  drainage  areas  of  rivers 
R  and  Q'.    6.  What  other  capture  may  be  predicted  ?    7.  Draw  a 
broken  [red]  line  along  the  divide  between  R  and  Q',  24  8.    8.  What 
other  capture  may  still  be  expected  ?    9.  Draw  a  full  [red]  line 
along  the  R-Q'  divide  after  this  capture  has  happened.    10.  Com- 
pare in  22  3  and  24  8  the  drainage  area  of  river  R ;  the  length  of 
the  eastern  branches  of  river  R ;  the  number  of  notches  in  which 
streams  run  through  hard-rock  ridges.     11.  Explain  (briefly)  the 
changes.    NOTE  :  When  a  stream  runs  through  a  notch  or  "  gap  " 
in  a  ridge,  the  notch  may  be  called  a  water  gap ;  when  no  stream 
runs  through  the  notch,  it  may  be  called  a  u-ind  gap.    12.  Print  T 
at  the  water  gaps  and   N   at  the  wind   gaps  in    24  7.    13.  What 
is  the  origin  of  the  chief  wind  gaps  ?     14.  Compare  in  22  4  and 
248  the  sharpness  of  the  divides  (or  "subdivides")  between  the 
branch  streams  ;  for  example,  the  subdivides  of  the  E.  branches  of 
R  on  formations  A  and  B.    15.  In  view  of  this  comparison,  what 
additional   statement   regarding   divides    may  be  made,  following 
that  of  §  3,  question  15  ?    NOTE  :  In  21 1  the  drainage  (by  rivers 
R  and  Q)  is  chiefly  transverse  (at  right  angles  to  the  general  trend 
of  the  ridges);  in  24  8  there  is  only  one  long  transverse  river,  and 
the  rest  of  the  streams  are  for  the  most  part  longitudinal  (parallel 
to  the  trend  of  the  ridges).    16.  Explain  (briefly)  how  the  change 
from  transverse  to  longitudinal  drainage  has  been  brought  about. 
17.   Of  the  two  originally  transverse  rivers,   R  and   Q,  21 1,  why 


THE  RIVER  CYCLE  93 

has  R  survived  ?  [18.  A  stream  which  increases  in  length  by 
headward  erosion  along  a  belt  of  weak  strata  may  be  classed  as 
subsequent.  19.  Mark  S  by  several  subsequent  streams  in  24  7  or 
24  8.  20.  Why  do  no  longitudinal  streams  run  along  the  resistant 
formations  ?]  [21.  The  Allegheny  mountains  of  Pennsylvania 
and  Virginia  offer  many  examples  of  longitudinal  and  transverse 
drainage,  similar  to  that  of  23  6,  24  7,  and  24  8.  22.  Locate  38  1  on 
Plate  40.  What  river  is  there  shown  ?  Is  its  course  longitudinal 
or  transverse  ?  23.  How  many  longitudinal  streams  are  shown  ? 
To  what  class  do  they  belong?  24.  The  lowest  contour  line  is 
400'  ;  the  contour  interval  is  100'.  Print  altitude  numbers  on  the 
contour  lines,  beginning  at  the  middle  of  the  S.  border  and  passing 
N.  to  the  N.  border.  25.  How  deep  are  the  valleys  below  the 
ridge  crests  ?] 

7.  1.  Compare  the  hard-rock  ridges  in  21 1  and  23  5  as  to  altitude  ; 
as  to  relief.  2.  What  has  caused  the  change  in  altitude  ?  in  relief  ? 
3.  Which  change  has  made  the  other  change  possible  ?  [4.  Draw 
a  K.— S.  profile  across  belts  C  to  G  of  24  8  in  23  6  c ;  draw  the  same 
profile  at  a  still  later  stage  of  erosion.]  5.  Compare  the  ridges 
of  23  5 -and  248  as  to  altitude;  as  to  relief.  6.  What  has  caused 
the  change  in  altitude?  in  relief?  [7.  In  23  6  a  the  uppermost 
profile  shows  the  form  of  ridges  E  and  C,  and  of  the  intermediate 
valley  D  for  23  5,  about  a  mile  E.  of  river  R  ;  complete  the  profiles 
for  23  6  and  24  7.  8.  Draw  earlier  profiles  for  stages  21  2,  22  3  and  4.] 
9.  Explain  (briefly)  how  the  wider  parts  (on  the  weaker  forma- 
tions) of  the  transverse  valley  R  in  21  2  and  22  3  have  grown  into 
longitudinal  valleys  in  23  6,  24  7  and  8.  10.  How  is  the  altitude  of 
a  longitudinal  valley  floor  related  to  the  altitude  of  the  next 
downstream  water  gap  in  the  inclosing  longitudinal  ridge  ?  Ex- 
plain. 11.  How  are  the  altitudes  of  several  neighboring  longitud- 
inal valley  floors  of  the  same  river  system  (as  D,  F,  H,  K,  247) 
related  to  each  other  ?  Explain.  12.  Is  there  a  corresponding  rela- 
tion in  the  altitudes  of  the  several  longitudinal  ridges  (as  E,  G,  J, 
24  7)  between  the  longitudinal  valleys  ?  Explain.  [13.  Complete 


94  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

ridge-and-valley  profile  k,  24  8  a.    Draw  an  earlier  ridge-and-valley 
profile  corresponding  to  stream  profile  n ;  draw  a  later  profile.] 

8.  [1.  38  1  shows  several   longitudinal  ridges  and  valleys.     In 
what  part  of  what  state  are  they  ?    To  what  mountains  do  they  be- 
long ?    2.  How  high  are  the  ridges  ?    (See  §  6,  question  25.)    3.  Are 
the  ridge  crests  even  or  serrate  (sawlike)  ?    4.  How  many  belts  of 
strong  and  weak  strata  are  here  included  ?    5.  What  is  the  origin 
of  the  notches  in  the  ridges  ?    6.  What  is  the  origin  of  the  longi- 
tudinal valleys  ?    7.  Which  figure  of  this  exercise,  Plates  21-24,  most 
nearly  exhibits  the  features  of  38  1  ?    8.  What  general  explanation 
can  you  give  for  the  ridges,  valleys,  and  notches  of  the  Allegheny 
mountains  ?      9.  A  fertile    longitudinal   valley  in  Virginia  (Shen- 
andoah  valley)  lies  next  ISTW.  of  the  Blue  ridge,  and  is  drained 
through  the  transverse  notch  or  gap  eroded  by  the  Potomac  river 
in  the  Bine  ridge:  Explain  the  origin  of  the  longitudinal  valley  in 
relation  to  the  Blue  ridge  and  the  Potomac  gap.] 

9.  [1.  What  is  the  attitude  (vertical,  steep  slanting,  gently  slant- 
ing)   of   the   ridge-making   formation    in  247  d?    in  7  e  ?    in  7  f? 
2.  Draw  in  these  figures  a  [red]  profile  for  each  ridge  after  its 
height  is  reduced  by  half  (the  level  of  the  neighboring  longitudinal 
valleys  remaining  little  changed).    3.  In  which  figure  has  the  ridge 
crest  changed  its  position  (to  right  or  left)  by  the  greatest  distance  ? 
by  the  least  distance  ?    Why  ?   4.  Draw  a  broken  [red]  line  along 
the   ridge  crests   C,  G,  L  in  23  5  and  6,  24  7  and  8.    5.  Why  may 
these  lines  be  called  longitudinal  divides  (or  subdivides)  ?    6.  Why 
do  the  more  important  longitudinal  divides  follow  the  strong  for- 
mations ?    7.  Draw  vertical  lines  in  the  same  figures  from  the  W. 
end  of  the  C,  G,  and  L  ridge  crests  (or  longitudinal  divides)  to  the 
sea-level  line  (see  235,  ridges   Oand  (7);  mark  off  on  a  strip  of 
paper  the  distance  from  the  SE.  corner  of  the  block  to  these  verti- 
cal lines.    8.  As  the  divides  are  lowered,  in  which  direction  has 
their  position  been  shifted  ?    Why  ?    9.  Which  one  has  changed 
most  ?    Why  ?    10.  Make  a  general  rule,  showing  how  the  shift  of 
a  wasting  ridge  crest  is  related  in  direction  and  amount  to  the 


THE   RIVER  CYCLE  95 

attitude  of  the  ridge-making  formation.  11.  Compare  the  cause  of 
this  kind  of  migrating  divide  with  that  of  the  kind  described  in 
§§  3  and  4.] 

10.  [1.  In  the  cycle  of  erosion  of  a  district  made  of  inclined 
formations,  resistant  and  weak,  which  of  the  formations  will  be 
soonest  worn  down  to   an   "  old "  appearance  (small  relief,  little 
above  sea  level)  ?    2.  How  much  may  the  resistant  formations  be 
worn  down  after  the  surface  form  of  the  weak  formations  is  "old  "  ? 
3.  What  will  the  surface  form  of  the  weak  formations  be,  when 
the  resistant  formations  are  worn  down  to  small  relief  ?    4.  In  the 
early  stages  of  a  cycle  of  erosion,  which  are  worn  down  the  faster, 
the  weak  formations  or  the  main  river  channels  ?    Explain.    Illus- 
trate by  one  of  the  figures  of  this  exercise.    5.  In  the  early  stages 
of  a  cycle,  which  formations  axe  worn  down  faster,  the  resistant  or 
the  weak  ?    Illustrate,  as  above.    6.  In  the  late  stages  of  a  cycle, 
which  formations  are  worn  down  the  faster  ?    Explain.    Illustrate, 
as  above.    7.  In  the  late  stages  of  a  cycle,  which  are  worn  down 
faster,  the  resistant  formations  or  the  river  channels  ?    Explain. 
Illustrate,  as  above.    8.  If  you  should  find  a  lowland  of  tilted  or 
disordered  strata  (like  21 1),  in  what  stage  of   a  cycle  of  erosion 
would  you  suppose  it  to  be  ?    9.  If  you  found  a  rather  even  high- 
land   (of   disordered   structure)   trenched    by    narrow,   steep-sided 
valleys,    what    stages    of   two  cycles    of   erosion  would   be   there 
represented?    10.  What  movement  of  the  earth's  crust  would  be 
supposed  to  have  taken  place  after  the  even  surface  of  the  region 
had  been  produced  ?    Explain.] 

11.  Define  :  §  3,  shift  or  migration  of  a  divide ;  §  4,  river  cap- 
ture, river  diversion,  captured  river,  diverted  river,  diverter,  be- 
headed river ;  §  5,  creeping  divide,  leaping  divide,  elbow  of  capture, 
misfit  stream  ;  §  6,  water  gap,  wind  gap,  subsequent  stream ;  §  7, 
transverse  valley,  longitudinal  valley ;  [§  9,  longitudinal  divide]. 


EXERCISE  IX.     SHORE  LINES 

OBJECT.  To  study  the  headlands,  cliffs,  bays,  and  other  features  of  a 
hilly  or  mountainous  coast. 

Preliminary.  The  series  of  eight  maps  in  this  exercise,  on 
Plates  27-29,  are  all  on  the  scale  of  1  :  80,000.  The  first  map,  27  1, 
shows  a  district  of  low  mountains  and  hills,  bordering  the  sea,  in 
part  shaded  with  hachures,  in  part  drawn  with  contours  (50'  in- 
terval). The  small  crosses  ( x  x )  in  the  water  area  represent  low 
rocky  ledges  or  reefs.  Depth  of  water  (in  feet)  is  indicated  at  sev- 
eral points.  (The  broken  lines  in  the  water  area  will  be  explained 
later.)  In  the  E.  part  of  the  map  the  rocks  are  resistant  and  the 
mountains  are  late  mature  or  subdued ;  in  the  N.  part  the  rocks 
are  weaker,  and  early  old  age  is  indicated  by  the  low  rounded 
hills  and  open  lowlands.  The  later  maps,  drawn  in  the  same  style, 
illustrate  changes  due  to  the  work  of  shore  waves  and  currents, 
and  to  movements  of  elevation  and  depression.  This  exercise  uses 

Plates  25,  27,  28,  29,  39. 

1.  1.  Suppose  the  land  in  27  1  to  sink,  or  the  sea  to  rise,  nearly 
100' ;  draw  a  [blue]  line  in  the  contoured  area,  to  show  the  new 
shore  line  thus  produced.  2.  What  effect  has  the  change  of  level 
on  bays  A  and  B  as  to  size  ?  as  to  general  shape  ?  on  the  length 
of  the  streams  entering  the  bays  ?  on  the  contoured  island  as  to 
size  ?  3.  How  many  headlands  or  peninsulas  are  converted  into 
islands  ?  Why  ?  4.  Why  are  three  hills,  between  bays  A  and  B, 
converted  into  small  low  islands  ?  5.  Where  are  new  peninsulas 
formed,  each  connected  with  the  mainland  by  a  narrow  isthmus  ? 
6.  Why  is  each  isthmus  narrower  than  its  peninsula  ?  7.  If  the 
land  had  been  submerged  150',  why  would  each  of  these  penin- 
sulas have  become  an  island?  each  isthmus  a  strait  (or  narrow 


SHORE  LINES  97 

water  passage)  ?  [8.  Add  contours  and  hachures  to  some  of  the 
unshaded  hills  and  valleys  in  27  1.  9.  The  scale  being  1 :  80,000, 
construct  a  linear  scale  5  mi.  long  in  the  lower  part  of  27  1.] 

2.  1.  Suppose  the  land  in  27  1  to  rise,  or  the  sea  to  sink,  about 
70' ;  mark  in  the  SE.  part  of  the  map  a  dotted  [blue]  line  to  show 
(as  well  as  you  can)  the  new  shore  line.    (This  new  line  may  be 
drawn  about  A"  from  the   present  shore  line.)    2.  What  effect   is 
thus  produced  on  the  length  of  the  headlands  ?    of  the  bays  ?    of 
the  streams  ?    on  the  breadth  of  the  isthmus  between  bays  C  and 
D  ?     3.  Why  are  two  islands   converted  into  peninsulas  ?  two 
straits  into  isthmuses  ?    some  rocky  reefs  added  to  the  mainland  ? 
4.  Suppose  the  land  in  27  1  once  to  have  stood  200'  higher  (or  the 
sea  200'  lower)  than  now ;  only  a  small  space  in  the  SW.  corner  of 
the  map  would  then  have  been  under  the  sea.    5.  Draw  in  broken 
[blue]  lines  (see  the  broken  guide-lines  in  27  1)  the  extended  rivers 
along  the  troughs  of  the  bays.    6.  Which  river,  A,  B,  C,  or  D,  was 
largest  ?    [7.  Draw  (roughly)  the  50',  100',  and  150'  contours  for 
the  valley  of  river  AB.~\     8.  In  view  of  all  this,  explain  the  origin 
of  the  shore  line,  as  it  is  drawn  in  27  1.     [9.  State  the  stage  — 
young,  mature,  or  old  —  reached  in  the  cycle  of  erosion  before  the 
change  of  level  which  produced  the  present  shore  line;  the  nature 
of  the  change  of  level  (rising  or  sinking  of  land).     10.  Estimate 
the  amount  of  the  change.] 

3.  1.  In  the  change  of  level  by  which  the  shore  line  of  27  1  was 
produced,  what  preexistent   forms  have  been  changed  into  large 
bays  ?    into  small  bays  (or  coves)  ?    wide  bays  ?    narrow   bays  ? 
headlands  ?      peninsulas  ?    isthmuses  ?    straits  ?    islands  ?    rocky 
reefs?    2.  Why  was  river   C  more    shortened  than   rivers  A,  B, 
or  D?    3.  Why  may  the  various  rivers  and  streams  as  drawn  in 
27  1  be  described  as  dismembered  by  submergence  ?   4.  Why  may  such 
a  coast  be  classed  as  embayed  ?    5.  Why  may  such  a  district  be 
described  as  partly  drowned?    6.  Why  do  the  dismembered  streams 
all  flow  into  bay  heads  ?    7.  Draw  a  [red]  line  along  the  divide 
between  bays  C  and  D;  between  bays  A  and  B.    Why  do  these 


98  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

divides   run   to   headlands  ?     8.  Why   are    some  headlands   round 
(as  on  NW.  side  of  bay  C)  ?  and  some  sharp  (either  side  of  bay  D)  ? 

4.  1.  During  the  slow  submergence  (hundreds  of  thousands  of 
years)  by  which  a  coastal  district  is  more  or  less  drowned  and  an 
embayed  shore  line  is  produced,  the  shore  waves  attack  the  sinking 
land,  sweeping  away  the  previously  weathered  soil  and  loosened 
rock.   2.  When  the  submergence  has  ceased,  the  attack  of  the  waves 
continues  at  the  level  then  reached.    3.  The  attack  is  especially 
strong  on  the  more  exposed  parts  of  the  coast.   Why  ?    4.  What  new 
features  will  be  thus  carved  ?    (DE,  310.7  ;  DP,  360.7 ;   G,  309.9  ; 
T,  211.3.)   5.  Draw  a  [red]  line  in  27  1  close  along  the  shore  where 
small  features  of  this  kind  have  already  been  produced.     (See  the 
darker,  ragged  parts  of  the  shore  line.)     6.  What  features  will  in 
time  be  produced  by  the  streams  at  the  bay  heads  ?     [7.  Has  the 
land  stood  in  its  present  position  as  long  as  it  stood  in  its  former 
position   (before   submergence)  ?    Explain.]     [8.  In  what  part  of 
what  state  is  the  coast  shown  in  39  1  ?    To  what  class  does  this 
coast  belong  ?    What  is  its  origin  ?    9.  Mark  a  [red]  line  across 
three  isthmuses.      10.  The  rocks  of  this  district  are  in  great  dis- 
order.    In  what  stage  of  erosion  was  the  district  just  before  sub- 
mergence took    place  ?      11.  Why  are    some   of   the   bays    called 
harbors  ?    Which  strait  is   called  a  river  ?    Which  upper  bay  is 
called  a  river  ?    12.  Draw  a   [blue]  line    through  each   of   three 
straits.    What  would  these  lines  have  represented  before  the  sub- 
mergence of  the  region  ?    13.  If  the  submergence  had  been  almost 
100'  greater,  into  how  many  islands  would  South  port  (island)  have 
been   divided  ?     Draw    its   shore   line    [blue]    in   that   condition. 
14.  Draw  [in  blue]  as  well  as  you  can  the  stream  system  of  Booth- 
bay  harbor  before  submergence.] 

5.  1.  25 1  is  a  block  diagram   (larger  scale  and  more  detailed 
than  27  1)  showing  a  low  sea  cliff  BE,  and  a  rock  bench  EC,  cut  by 
strong  waves  on    a   sloping  coast,   like  that   SE.   of   bay  D,  27  1. 
2.  What  different  conditions  of  tide  and  weather  are  shown  in  the 
three  parts  of  25  1  ?    (DE,  119.8 ;  DP,  83.4 ;   G,  290.2 ;   T,  187.3.) 


SHORE   LINES  99 

3.  About  how  high  is  the  cliff  (see  scale  at  right  corner)  ?  4.  What 
is  the  tidal  range  (in  feet)  here  indicated  ?  5.  How  wide  is  the 
rock  bench  EC  between  the  cliff  base  and  the  low-water  shore  line? 
G.  What  is  the  relation  of  the  sea  level  at  high  tide  to  the  cliff  ? 
[7.  Prolong  the  profile  line  AB  to  low-water  level  a  little  outside 
of  C  ;  from  the  intersection  of  the  profile  and  the  low-water  line 
draw  a  [red]  line  (about  parallel  to  the  block  front,  outside  of  the 
rock  bench)  to  show  the  initial  shore  line  (as  if  the  sea  had  not  cut 
any  cliff  in  the  land  slope).  8.  Which  is  the  more  irregular,  the 
initial  shore  line  or  the  present  shore  line  ?  Explain.]  9.  Why  is 
there  so  little  rock  waste  at  the  base  of  the  sea  cliff?  10.  Where 
has  much  of  the  coarser  waste  been  deposited  ?  11.  Where  has  most 
of  the  fine  waste  been  deposited  ?  NOTE  :  On  the  narrow,  wave- 
cut  rock  bench  of  a  bold,  exposed  coast,  little  rock  waste  is  carried 
by  waves  and  currents  along  the  shore,  because  the  waste  is  soon 
swept  off  into  comparatively  deep  water.  12.  In  calm  weather  the 
sea  water  on  a  rocky  coast  is  very  clear.  Why  does  it  become  some- 
what turbid  in  stormy  weather  ?  [13.  Explain  the  origin  of  the 
two  sea  caves  in  the  cliff  of  the  low-tide  part  of  25  1 ;  of  the  rock 
a r <'li  in  the  high-tide  part;  of  the  little  cove  (just  beyond  the  rock 
arch)  ;  of  the  narrow  chasm  (this  side  of  the  rock  arch) ;  of  the  out- 
standing stack  (in  the  farther  part,  showing  storm  waves) ;  of  the 
skerries  (small  rocks  or  minute  islands  in  the  high-tide  part) ;  of 
the  heap  of  rock  waste  (where  high-tide  and  low-tide  parts  join).] 
14.  Where  is  the  rock  structure  indicated  ?  Is  it  horizontal  or  dis- 
ordered ?  !.">.  Why  may  the  district  of  which  25  1  is  a  part  be 
described  as  "  well-subdued  mountains  with  a  very  young  shore 
line."  16.  What  change  will  the  sea  cliff  suffer  if  the  storm  waves 
continue  to  cut  away  its  base  ? 

6.  1.  Draw,  on  the  near  end  of  25  1,  a  profile  at  M,  parallel  to 
BE,  to  show  the  position  of  the  sea  cliff  after  it  has  been  worn 
farther  back.  2.  From  the  base  of  cliff  M  draw  a  rock-bench  profile 
parallel  to  EC.  [3.  How  high  is  the  new  cliff  M  ?  How  wide  is 
its  rock  bench  ?  How  far  has  cliff  M  retreated  from  cliff  B  ? 


100  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

4.  Indicate  between  C  and  D  a  new  deposit  of  rock  waste  (about 
as  much  as  is  shown  at  D}.  5.  What  effect  has  this  deposit  on  the 
depth  of  the  water  between  C  and  D  ?  NOTE  :  During  storms  the 
loose  material  on  the  sea  bottom  is  agitated  at  depths  of  100' 
or  more.  6.  What  effect  will  this  agitation  have  on  the  texture  of 
the  sea-bottom  waste  ?  7.  What  will  become  of  the  "  grindings  "  ?] 
8.  Draw  the  profile  for  the  cliff,  bench,  and  bottom  deposit  for 
point  N?  9.  As  the  cliff  is  cut  back,  what  change  takes  place  in 
its  height  ?  in  the  width  of  the  rock  bench  ?  10.  What  effect  will 
the  new  height  of  the  cliff  have  on  the  amount  of  rock  waste 
weathered  from  it?  11.  What  effect  will  the  new  width  of  the 
bench  have  on  the  strength  of  the  waves  at  the  cliff  base  ?  NOTE  : 
As  these  changes  go  on  along  the  shore,  there  comes  a  time  when 
so  much  waste  is  supplied  from  the  weather-beaten  cliffs  that  it 
cannot  all  be  quickly  swept  away  into  deeper  water  by  the  weak- 
ened waves  ;  a  sheet  of  coarse  and  fine  waste  .thus  comes  to  spread 
over  more  or  less  of  the  rock  bench.  That  part  of  the  waste  sheet 
which  is  bare  at  low  tide  is  called  a  beach. 

7.  1.  252  is  a  general  view  of  a  shore  line  on  a  smaller  scale 
than  25 1,  but  on  a  larger  scale  than  27  1.  2.  How  high  is  the  cliff 
QR  in  25  2  ?  How  wide  is  the  beach-covered  rock  bench  RL  ?  How 
thick  is  the  beach  deposit  at  L  ?  3.  Does  25  2  represent  a  more  or 
a  less  advanced  stage  of  shore  development  than  25  1  ?  Explain. 
4.  The  rock  bench  is  now  so  wide  that  some  of  the  beach  material 
(cobbles,  gravel,  sand),  when  agitated  by  storm  waves,  is  slowly 
shifted  along  shore  by  the  local  current.  5.  Does  the  beach  mate- 
rial come  from  the  shore  cliffs  or  from  the  inland  valleys  ?  Ex- 
plain. 6.  In  which  direction  in  252  has  the  beach  material  been 
shifted?  How  can  you  tell?  7.  Why  may  ST  be  described  as  a 
barrier  beach  (or  sand  and  gravel  reef)  inclosing  part  of  an  initial 
embayment  ?  8.  Has  the  barrier  beach  (or  reef)  been  built  up  from 
the  bottom  or  forward  from  one  end?  (See  25 3,  a  cross  section 
showing  lines  of  reef  growth.)  [9.  In  which  part  of  the  barrier 
beach  is  it  thickest  ?  10.  How  deep  was  the  water  originally  at 


SHORE   LINES  101 

the  mid-point  of  the  reef  ?  (Join  the  hill  slopes  QS  and  UT  by  a 
curved  line  to  show  the  original  depth  of  the  bay  between  the  hills  ; 
estimate  the  depth  of  the  curve  below  the  high-tide  shore  line.) 
NOTE  :  The  height  of  the  reef  is  increased  by  the  action  of  storm 
waves,  which  may  throw  up  cobbles  and  pebbles  in  a  ridge  10'  or 
20'  above  high  tide.  11.  Estimate  the  thickness  of  the  reef  ST  at 
its  middle.] 

8.  1.  At  which  end  of  the  reef  ST  in  25  2  is  a  passage  or  inlet  kept 
open  ?    2.  What  does  the  position  of  the  inlet  indicate  as  to  the 
general  direction  of  the  longshore  currents  ?   3.  In  what  direction 
will  a  tidal  current  flow  through  the  inlet  while  the  tide  is  slowly 
"  falling"  on  (withdrawing  from)  the  beach?    while  the  tide  is 
slowly  "  rising  "  (advancing)  on  the  beach  ?    4.  What  name  is  given 
to  these  tidal  currents  ?     For  about  how  many  hours  does  each 
current  run?     (DE,  119.9;  DP,  83.8;    T,  187.7.)    5.  What  sort  of 
material  will  be  carried  into  the  inclosed  bay  or  lagoon  by  the  inflow- 
ing current  when  the  sea  water  is  turbid  during  storms  ?    6.  What 
will  become  of  this  material  in  the   quiet  water  of   the  lagoon  ? 
7.  What  effect  will  be  thus  produced  on  the  size  of  the  lagoon  ? 
NOTE  :  A  deposit  of  fine  silt,  mixed  with  decaying  plant  material, 
is  formed  on  the  bottom  and  around  the  border  of  a  lagoon ;  when 
it  is  built  up  to  high-tide  level  and  has  salt  grass  growing  on  it, 
it  is  called  a  tide  marsh.     8.  Shade  [light  red]  the  sand  and  gravel 
reef  ST,  and  [light  blue]  the  lagoon  A  ;  dot  [blue]  the  tide  marsh 
TM.    9.  Draw   a    [blue]    line    around   the   original  shore  of   the 
inclosed  bay ;  prolong  this  line  seaward  from  S  and  T.    10.  Draw 
a  similar  [blue]  line  around  the  original  shore  of  bay  B  ;  draw  a 
[blue]  line  to  indicate  the  original  shore  line  of  hill  U.     (See  the 
dotted  line,  showing  the  original  sea   bottom,  in  front  section.) 
11.  How  was  the  original  shore  line  produced  ?    [12.  In  what  stage 
of  erosion  was  the  region  before  the  original  shore  line  was  thus 
formed?] 

9.  1.  When  a  reef   extends  only  part   way  across  a  bay,  it  is 
called  a  spit.     Where  is  a  spit  shown  in  25  2  ?    Why  may  it  be 


102  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

called  a  hooked  spit  ?  2.  Does  much,  waste  from  cliff  U  now  go 
to  the  beach  of  cliff  A'  ?  from  cliff  Q  to  the  spit  of  bay  B  ?  (Beach 
material  may  be  swept  past  a  narrow  tidal  inlet  on  the  shallow 
bottom  formed  by  the  extension  of  the  beach  material  offshore.) 
[3.  What  accident  has  happened  along  the  face  of  cliff  U  ?  4.  Did  it 
take  place  lately  or  a  long  time  ago  ?  Why  ?  (Extensive  landslides 
of  this  kind  took  place  on  the  S.  coast  of  England  in  1839.)] 
5.  What  part  of  25  2  best  indicates  the  general  outline  which  the 
shore  had  before  the  cliff,  spits,  and  reefs  were  formed  ?  6.  Was 
the  original  outline  more  or  less  irregular  than  the  present  outline  ? 
7.  When  a  shore  line  is  in  the  stage  represented  by  25  1,  is  its 
irregularity  greater  or  less  than  in  the  initial  stage  ?  than  in  the 
stage  of  25  2  ?  [8.  When  the  cliffs  Q,  U,  X  in  25  2  have  been  cut 
back  about  200'  farther,  what  will  have  happened  to  the  reef  ST? 
to  the  hooked  spit  of  the  bay  B  ?  9.  Draw  the  shore  line  and 
the  cliff  crests  [red]  in  that  stage ;  shade  [red]  the  cliff  faces. 
10.  Draw  the  shore  line  and  the  cliff  crests  [blue]  when  the  shore 
has  been  cut  back  to  W;  shade  the  cliffs  [blue].]  11.  Will  the  later 
changes  in  25  2  make  the  shore  line  more  or  less  irregular  than 
now  ?  12.  Will  the  extent  of  shore  line  bordered  by  cliffs  increase 
or  decrease  ?  13.  Let  the  term  fully  mature  be  applied  to  a  shore 
line  that  has  been  cut  back  of  all  the  initial  bay  heads.  Do  cliffs 
form  a  greater  fraction  of  the  shore  line  in  such  a  stage  than  in 
the  stage  of  25  2  ?  14.  Compare  in  a  general  way  the  shore-line 
features  of  the  initial  stage,  of  early  youth  (25  1),  of  early  maturity 
(25  2),  and  full  maturity.  [15.  Which  is  greatest,  the  retreat  of  a 
cliff  or  the  wearing  down  of  the  rock  bench  in  front  of  it  ?  Why  ? 
16.  How  is  the  depth  of  the  sea  in  deep  water  offshore  from  a  cliff 
affected  by  the  cutting  of  the  shore  cliffs  ?] 

10.  1.  In  27  2  sea  cliffs  are  indicated  by  heavy  hachures  along  the 
more  exposed  parts  of  the  coast  (the  cliffs  are  given  more  breadth 
than  they  should  have,  in  order  to  make  them  distinct)  ;  spits  and 
reefs,  by  dotted  belts  at  bay  mouths  ;  deltas  and  tidal  marshes,  by 
dotted  spaces  at  bay  heads  and  on  bay  sides.  The  high-water  shore 


SHORE  LINES  103 

is  a  heavy  line ;  the  low-water  shore  is  a  lighter  line  (omitted  where 
the  ragged  rock  bench  has  no  beach).  2.  Compare  27  1  and  2, 
beginning  at  SE.  corner,  and  state  how  27  2  differs  from  27  1  along 
the  outer  coast  SE.  of  bay  D  •  at  the  entrance  to  the  two  E.  branches 
of  bay  Z>;  in  the  larger  island  on  the  NW.  side  of  bay  D;  in  the 
outer  island  between  bays  D  and  C  ;  in  the  peninsula  between  bays 
D  and  C  ;  along  the  NW.  side  of  the  isthmus  of  this  peninsula ;  in' 
the  island  between  bays  C  and  B  ;  in  the  two  small  bays  NE.  of 
this  island ;  between  the  inner  and  outer  parts  of  bay  B  and  of 
bay  A  ;  in  all  the  bay  heads.  3.  Is  the  shore  line  of  the  spits  and 
reefs  at  the  bay  mouths  convex  or  concave  to  the  sea?  4.  Shade 
[light  blue]  in  27  2  the  space  where  the  sea  has  cut  away  the  land. 
(The  initial  shore  line  of  27  1  is  partly  indicated  by  dotted  lines 
in  27  2.)  5.  Shade  [light  red]  in  27  2  the  reefs,  inclosed  lagoons, 
deltas,  and  tidal  marsh. 

11.  1.  Why  may  the  island  on  the  NW.  side  of  bay  D,  27  1,  be 
described  in  27  2  as  a  land-tied  island  remnant  ?  2.  Compare  its 
isthmus  with  that  of  the  DC  peninsula,  in  27  1,  as  to  origin  and 
material ;  with  the  isthmus  of  the  land-tied  island  between  bays 
C  and  B,  27  2,  as  to  shape.  3.  There  is  a  small  land-tied  island  at 
the  head  of  bay  C,  27  2 ;  compare  the  manner  of  its  becoming  tied 
to  the  mainland  with  that  of  the  other  land-tied  islands.  [4.  Part 
of  the  original  NE.  branch  of  bay  C,  27  1,  is  now  inclosed  ;  com- 
pare the  method  of  its  inclosure  with  that  of  the  small  inclosed  bay 
heads  (lagoons)  on  the  NW.  side  of  the  entrance  to  bay  C.  NOTE  : 
Lagoons  that  are  not  entirely  inclosed  receive  the  salt  water  of 
flood  tide  through  their  inlets.  Lagoons  that  are  inclosed  usually 
become  fresh,  as  the  original  salt  water  slowly  flows  out  through 
the  sand  reef  and  is  replaced  by  water  from  the  land.  5.  Mark 
in  27  2  two  salt  lagoons,  S  ;  two  fresh  lagoons,  F.  6.  Show  by  [blue] 
arrows  the  direction  in  which  reef  material  has  been  drifted  by 
waves  and  currents  in  the  spits  on  the  E.  side  of  bay  D  ;  in  the 
spits  between  the  outer  and  inner  parts  of  bay  B,  and  of  bay  A  ; 
in  the  reefs  back  of  the  land-tied  island  remnant  between  bays  C 


104  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

and  B.    7.  Has  the  coarser  waste  generally  been  drifted  landward 
or  seaward  ?    Why  ?] 

12.  [1.  Complete  27  2  a  (with  hachures,  etc.),  so  that  it   shall 
show  three  reef-inclosed  lagoons,  one  double-tied  island  remnant 
with  a  lagoon  behind  it,  and  one  vanishing   island   with    a   spit 
behind  it.    2.  Complete  27  2  b  (in  contours,  etc.),  so  as  to  show  two 
reef-inclosed  lagoons,  with  small  deltas  at  their  heads,  and  a  200' 
cliff  at  the  end  of  the  middle  headland.    What  is  the  contour  in- 
terval ?    3.  Complete  27  2  c,  so  as  to  show  the  initial  bay  heads  and 
the  new-formed  deltas  in  proper  relation  to  the  streams,  and  two 
spits  nearly  inclosing  the  bay  ;  also  (in  broken  lines)  the  former  river 
system  here  dismembered  by  drowning.    4.  Complete  27  2  d,  showing 
two  delta-tied  islands  and  two  delta-inclosed   lakes.     5.  Tidal  cur- 
rents are  stronger  in  bays  than  on  the  outer  shore  line.    The  inflow- 
ing tidal  current,  or  flood  tide,  of  bay  C,  27  2,  is  indicated  by  curved 
dotted  lines.    6.  The  finer  shore  waste,  when  agitated  by  waves,  is 
slowly  drifted  inward  by  the  flood  current ;  spits  pointing  inland 
may  be  thus  formed.     Print  T  by  three  such  spits  in  bay  C,  27  2.] 
[7.  In  what  part  of  what  state  is  the  district  of  39  2  ?    8.  Mark 
[red]   lines  along  the   outside  of   five  barrier   beaches,   inclosing 
lagoons.    9.  Do  the  lagoons  behind  these  beaches  occupy  all  of  the 
original  bay  heads  ?    Explain.     10.  Mark  short  [red]  hachures  (as 
in  27  2)  where  you  think  sea  cliffs  have  been  cut.    11.  What  name 
is  given  to  a  land-tied  island  ?    12.  Draw  a  heavy  [blue]  line  to 
show  the  remaining  parts  of  the  original  shore  line.     13.  Is  the 
present  shore  line  on  the  whole  more  or  less  irregular  than  the 
original  shore  line  ?    14.  How  was  the  original  shore  line  pro- 
duced ?    15.  What  was  the  previous  general  form  of  the  hills  and 
valleys  in  this  district  ?    16.  Draw  in  39  2  the  original  outline  of 
the  shore  line.] 

13.  1.  What  is  the  chief  difference  between  the  shore  lines  of 
27  2  and  28  3  ?    2.  In  the  change  from  27  2  to  28  3,  why  has  the 
SE.  cliff  increased  in  height  ?     3.  Why  have  two  lagoons  of  bay  D 
been  changed  to  tidal  rivers  ?    NOTE  :  Tidal  rivers  are  very  broad 


SHORE  LINES  105 

in  proportion  to  their  length,  because  their  volume  is  supplied  by 
flood  tide  from  the  ocean,  instead  of  by  rainfall  on  the  land ;  their 
current  changes  direction  with  the  ebb  and  flow  of  the  tide. 
4.  Why  has  the  third  lagoon  of  bay  D  disappeared?  5.  What  has 
happened  to  the  land-tied  island  remnant  and  to  the  vanishing  pen- 
insula N.  of  bay  D,  27  2  ?  to  the  three  islands  in  the  upper  part 
of  bay  C,  27  2  ?  to  the  delta  of  river  C  ?  to  the  three  lagoons  of 
the  CB  headland  ?  to  the  upper  parts  of  bays  B  and  A  ? 

14.  [1.  What  reason  may  be  found  in  the  form  of  27  1  to  suggest 
that  the  rocks  around  the  bay  heads  A  and  B  are  much  weaker  than 
those  about  bay  D  ?  and  that  the  rocks  of  the  hilly  peninsulas  in- 
closing bay  B  are  of  intermediate  hardness  ?  2.  As  long  as  pebbles 
and  sand  are  supplied  from  the  cliffs  of  the  peninsulas,  what  forms 
will  be  built  farther  up  bays  B  and  A  ?  (See  27  2.)  3.  When  the 
peninsulas  are  consumed  (as  in  28  3)  and  the  weak  rocks  then  ex- 
posed yield  only  fine  waste  to  the  cliff-cutting  waves,  where  will 
(most  of)  the  fine  waste  be  swept  ?  4.  In  the  absence  of  protect- 
ing barrier  beaches,  will  the  bay  mouths  be  narrowed  or  widened 
by  wave  action  ?  Will  the  bay  heads  be  enlarged  by  wave  action  or 
filled  with  tide  marsh  ?  5.  How  wide  are  the  low-tide  mud  flats 
at  the  head  of  bays  A  and  B,  28  3  ?  6.  Compare  these  changes  of 
bay  heads  A  and  B  with  those  of  the  two  small  branch  bays  on 
the  E.  side  of  bay  D.  7.  What  is  the  origin  of  the  small  island 
between  bays  A  and  B,  283?]  8.  How  far  back  have  some  of  the 
headlands  been  cut  in  28  3  ?  (The  initial  shore  line  is-  indicated  in 
28  3  by  single  dots  ;  the  shore  line  of  27  2  by  double  dots.)  9.  How 
far  has  the  delta  of  river  C  been  built  forward  ?  10.  How  many 
islands  have  been  tied  to  the  mainland  thereabouts  ?  11.  Compare 
the  shore  lines  of  27  1,  27  2,  and  28  3  as  to  length,  height,  and  con- 
tinuity of  cliffs  ;  as  to  length  and  continuity  of  beaches  ;  as  to  num- 
ber of  islands ;  of  lagoons ;  as  to  length  of  headlands  (from  bay 
heads)  ;  as  to  general  irregularity  of  outline ;  as  to  the  number  of 
natural  harbors  for  large  vessels  (drawing  20'  or  more)  and  for 
small  vessels  (drawing  not  more  than  5'). 


106  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

15.  [1.  Locate  a  city  near  the  mouth  of  river  C,  28  3.     Where 
would  you  place  a  lighthouse  near  the  entrance  to  bay  C  ?    Mark 
it  LH.    2.  Draw  in  28  3  a  the  shore  lines  for  three  successive  stages 
(see  the  guide  lines ;  draw  the  first  shore  line  dotted ;  the  second, 
broken ;  the  third,  full)  ;  for  the  third  outline  indicate  the  cliffs, 
sand  reefs,  etc.,  as  in  27  2  and  28  3.    3.  In  the  first  outline,  how 
many  small  bays  are  partly  inclosed  by  spits  ?  wholly  inclosed  by 
reefs  ?    4.  In  the   second  outline,  how  many  lagoons  have  been 
filled  ?     how  many  destroyed  by  retreat  of  cliffs  to  lagoon  head  ? 

5.  In  the  third  outline,  how  many  bays  have  disappeared  entirely  ? 
how  many  remain  as  lagoons  more  or  less  filled  with  tide  marsh  ? 

6.  In  28  3  b  draw  a  new  shore  line  showing  changes  such  as  have 
happened  to  bays  A  and  B  in  28  3.    Indicate  the  shore  cliffs  and  the 
low-tide  line.    How  wide  are  the  low-tide  mud  flats  ?    7.  In  28  3  c 
note  that  the  largest  river  enters  the  W.  branch  of  the  N.  bay  ;  let 
these  bay  heads  be  many  miles  from  the  exposed  outer  shore  line. 
Draw  three  successive  delta  outlines  for  the  seven  streams.    In  the 
third  outline,  what  has  happened  as  to  island  tying  ?    as  to  bay 
closing  ?  as  to  river  lengthening  (for  the  largest  river)  ?] 

16.  1.  Compare  28  3  and  4,  as  to  irregularity  of  shore  line.    2.  In 
what  part  of  28  4  has  the  shore  line  been  most  simplified  in  the 
change  from  28  3  ?     (The  outline   in  28  3  is   indicated  in  28  4  by 
three-dot  lines.)    3.  Are  the  beaches  more  or  less  continuous  than 
before  ?     Explain.    4.  Where   are  the  beaches  still   interrupted  ? 
Why  ?    5.  Where  is  the   broadest  space  between  high-  and   low- 
water  lines  ?    Why  ?    6.  Why  has  the  first  SE.  cliff  retreated  more 
than  the  second  SE.  cliff  ?  the  fifth  less  than  the  fourth  ?    7.  Are 
the  cliffs  of  28  4  generally  higher  or  lower  than  the  cliffs  of  28  3  ?  of 
27  2  ?  of  27  1  ?    Why  ?    8.   In  28  4  a,  will  further  retreat  of  the  cliffs 
give  them  a  greater  or  a  less  height  ?    Explain.    9.  Are  any  cliffs  of 
decreasing  height  shown  in  28  4  ?    Mark  —  in  front  of  them  ;  mark 
-fin  front  of  the  cliffs  of  increasing  height.    10.  In  which  of  the 
four  stages  of  shore-line  development  27  1,  2,  28  3,  4,  are  protected 
harbors  most  common  ?    Why  ?     [11.  The  coast  of  California  for 


SHORE   LIXES  107 

many  miles  K.  and  S.  of  the  Golden  Gate  is  about  as  harborless 
as  the  coast  of  28  4.J 

17.  [1.  Imagine  some  wet-weather  streams  flowing  W.  between 
the  foreground  hills  of  28  4  a.    Why  may  they  be  described  as  be- 
headed  by  cliff  retreat  ?    2.  Draw  some  dotted  [blue]  lines  in  28  4 
to  show  similarly  beheaded  wet-weather  streams.    3.  Examine  28  4  b. 
Is  the  small  stream  that  comes  down  from  the  background  hills  as 
long  as  it  used  to  be  ?    Explain.    4.  Why  may  such  a  stream  be 
described  as  betrunked  by  cliff  retreat  ?    5.  Mark  BC  at  the  mouth 
of  such  a  stream  in  the  NW.  part  of  28  4.    6.  Does  the  stream  of 
2846  enter  the  sea  at  grade  (in  accordant  fashion),  or  by  a  hanging 
mouth  (in  discordant  fashion)  ?     7.  Are  the  streams  of  such  hang- 
ing valleys  likely  to  be  large  or  small  ?  ^Explain.    8.  Compare  this 
case  with  that  of  the  side  streams  in  the  mountain  gorge,  Exercise 
V,  §  12,  question  9.    9.  Mark  H  by  the  mouth  of  a  hanging  valley 
in  the  E.  part  of  28  4 ;  in  1 1.    10.  The  dotted  lines  on  the  sea 
surface  of  28  4  a  represent  the  crests  of  successive  waves  driven 
by  an  E.  wind.    Where  do  they  first  break  on  the  beach  ?   Why  ? 
11.  How  does  the  breaking  wave  then  advance  along  the  beach  ? 
Why  ?     12.  Why  would  a  man  standing  on  the  cliff  top  hear  a  con- 
tinuous "  roar  "  from  a  series  of  wind-driven  waves  ?    Compare  the 
regular  advance  of  such  wind-driven  waves  along  the  beach  in  28  4  a, 
with  the  arrival  of  a  wave  on  the  coast  of  25  2.    NOTE  :   In  calm 
weather  the  advancing  swell  of  a  distant  storm  adjusts  itself  to 
the  curves  of  a  mature  shore  line,  and  falls  over  in  surf  almost 
simultaneously  for  distances  of  half  a  mile  or  more.     13.   How 
does   the  sound  of  such  surf  differ  from  that  of  the  wind-driven 
waves  of  question  12?] 

18.  [1.  Compare  the  sea  cliffs  of  28  4  with  the   cliffs  in  the 
canyon  of  Exercise  IV,  as  to  relation  to  baselevel  (sea  level)  ;  as 
to  relation  to  structure  (the  structure  of  the  land  mass  in  28  4  may 
be  taken  to  be  similar  to  that  of  25  1)  ;  as  to  uniformity  of  height 
(from  base  to  top)  ;  as  to  occurrence  of  talus  (the  active  attack  of 
the  waves  at  the  base  of  a  sea  cliff  prevents  the  accumulation  of 


108  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

much  talus  along  the  shore  line)  ;  as  to  change  in  height  of  cliff 
face  with  advancing  development ;  as  to  change  in  plan  or  pattern 
(as  seen  on  a  map)  with  advancing  development.] 

19.  1.  Compare  the  shore  line  of  29  5  and  28  4  as  to  regularity 
(or  simplicity)  of  outline ;  as  to  continuity  of  cliff  front ;  as  to  con- 
tinuity of   beaches.     2.  Explain  the  differences.     3.  In  what    re- 
spects may  the  shore  line  of  29  5  be  called  "  more  fully  mature " 
than  that  of  28  4  ?    [4.  Mark  H  opposite  the  mouths  of  two  hanging 
valleys    in  29  5.]     5.  Compare  the    hilltop    heights   along  the   N. 
borders  of  28  4  and  29  5.    (The  contour  interval  is  50'.)    6.  Which 
is  more  rapid,  marine  erosion  along  the  shore  line,  or  subaerial 
weathering  of  the  hills  ?    7.  In  29  5  a  stream  flows  SE.  (in  NW. 
part  of  figure) ;  compare  in  27  1  and  29  5  its  fall  (feet  per  mile), 
and  the  form  (openness)  of  its  valley.    8.  Explain  the  differences. 

9.  Shade  [light  blue]  the  area  of  lost  land  in  the  SE.  part  of  29  5. 

10.  While  the  hills  have  been  (slowly)  worn  down  by  weathering, 
and  the  shore  line  has  been  (more  rapidly)  worn  back  by  the  waves, 
what  has  happened  to  the  rock  bench  offshore  ?    NOTE  :  The  down- 
wearing  of  a  rock  bench,  a  mile  or  more  offshore,  cannot  be  very 
rapid ;    but  it  must  proceed  as  long  as   storm  waves   effectively 
jostle  and  grind  the  waste  that  lies  on  it.     [11.  Why  will  the  outer 
(offshore)  part  of  a  rock  bench  be  worn  deepest  ?    12.  The  depth 
of  the  water  in  29  5  along  the  original  outer  shore  line,  SE.  of  bay 
D,  27  1,  may  now  be  about  80' ;  at  the  original  headland  between 
the  two  E.  branches  of  bay  D,  27  1,  50'.    The  drowned  valley  of 
river  Z),  27  1,  may  now  be  partly  filled  with  land  waste,  so  that  its 
depth  at  the  inner  and  outer  ends  of  the  broken  line  in  29  5  is  60' 
and  80'.    13.  Enter  these  depths  on  29  5  (several  depths  are  already 
indicated  there).    14.  Draw  sea-bottom  contours  in  SE.  part  of  29  5 
for  50'  and  100'.    15.  Do  these  contours  indicate  that  the  surface 
there  is  smoother  or  rougher  than  the  corresponding  surface  of 
2Tl?    Explain.] 

20.  1.  In  what   respects  does  29  6  resemble  29  5  ?    2.  Draw  in 
29  6  a  [blue]  line  corresponding  to  the  mature  cliff  line  of  29  5. 


SHORE   LINES  109 

3.  The  broken  lines  in  206  are  contours  for  50',  100',  and  150'. 
What  movement  (elevation  or  depression  of  the  region  with  respect 
to  sea  level)  has  taken  place  since  295?  4.  Did  the  movement 
occur  soon  after  or  long  after  the  stage  of  shore-line  development 
shown  in  29  5  ?  5.  What  is  the  present  altitude  of  the  former 
shore  line  in  the  SE.  part  of  29  6  ?  in  the  NW.  part  ?  6.  Was  the 
movement  by  which  29  5  was  changed  to  29  6,  of  uniform  amount 
in  all  parts  ?  7.  How  did  it  vary  ?  8.  What  name  may  the  new 
land  area  be  given  ?  9.  In  what  exercise  have  land  forms  of  this 
kind  been  already  studied  ?  10.  In  what  stage  of  development  is 
the  new  land  form  of  29  6  ?  Why  ?  11.  Print  B,  C,  D  on  the  rivers 
of  29  6  corresponding  to  three  bays  of  27  1.  12.  Why  does  such  corre- 
spondence exist?  13.  AVhy  may  the  rivers. on  the  coastal  plain  of 
29  6  be  classed  as  consequent  ?  14.  Why  may  they  be  described  as 
extended  by  emergence  (or  elevation)  ?  15.  How  many  streams  of 
29  5  are  now  united  in  river  D  ?  16.  Why  may  these  streams  be 
described  as  engrafted  by  emergence  (or  elevation}  ?  17.  What  con- 
trasted description  was  suggested  for  the  streams  of  27  1  ?  (See 
§  3.)  [18.  To  what  class  of  land  forms  does  the  land  of  29  5 
belong  ?  (The  structure  of  the  land  may  be  taken  as  similar  to 
that  shown  in  25  1  and  2.)  19.  In  what  stage  of  development  is 
the  land  area  of  29  5  ?  of  27  1  ?  of  the  NE.  part  of  29  6  ?  (As  to  29  6, 
note  whether  the  inland  area  is  still  in  the  same  cycle  of  erosion 
with  the  two  preceding  figures,  or  whether  that  cycle  has  been  in- 
terrupted by  elevation  and  a  new  cycle  thus  introduced.)  20.  Com- 
pare the  sea  cliff  of  29  5  with  the  elevated  sea  cliff  of  29  6,  as  to 
altitude  of  baseline  ;  as  to  amount  of  talus  at  the  base  ;  as  to  steep- 
ness of  cliff  face.  21.  Elevated  sea  cliffs  occur  at  several  different 
levels  around  the  E.  end  of  Cuba.  What  does  this  indicate  ?] 

21.  NOTE  :  29  5  a,  b,  c,  d,  represent,  in  block  diagrams,  the 
changes  in  the  shore  line  of  a  low  coastal  plain  of  weak  (imperfectly 
consolidated)  strata,  fronting  on  a  shallow  ocean  margin.  The 
initial  profile  of  the  land  and  sea  bottom  is  shown  by  a  full  (or 
broken)  line.  Slopes  are  much  exaggerated.  1.  While  a  very  low 


110  EXERCISES   IX   PHYSICAL   GEOGRAPHY 

"cliff"  is  worn  at  k,  29  5  a,  what  has  taken  place  at  n  ?  at  m  ? 
NOTE  :  In  a  shore  of  this  kind  the  water  is  so  shallow  that  little 
of  the  storm-wave  strength  is  spent  on  the  land  border ;  more  of 
it  is  spent  in  agitating  the  loosened  material  at  a  moderate  dis- 
tance offshore,  as  about  n.  The  coarser  material  is  slowly  shifted 
landward  and  forms  a  shoal,  as  at  m ;  eventually  the  shoal  is  built 
up  above  sea  level,  forming  a  reef,  and  inclosing  a  lagoon ;  sand 
is  blown  from  the  reef  beach  into  the  lagoon,  and  the  reef  is 
broadened.  2.  Draw  the  outline  of  a  narrow  reef  on  the  sea  sur- 
face of  29  5  a,  and  mark  it  R ;  mark  the  inclosed  lagoon  L.  3.  The 
finer  material  shifted  from  n  is  carried  seaward  and  deposited  some 
distance  offshore,  beyond  q.  4.  Where  is  the  sea  bottom  thus  deep- 
ened ?  where  made  less  deep  ?  5.  How  does  the  reef  in  2<)  5  b  differ 
from  the  reef  drawn  in  29  5  a  ?  6.  Where  has  the  material  for  the 
widened  reef  come  from  ?  7.  How  has  it  been  carried  ?  8.  How 
has  the  depth  changed  at  n  ?  at  q  ?  Why  ?  9.  How  has  the 
width  of  the  lagoon  been  changed  from  29  5  a  to  5  b  ?  10.  How  is 
the  tide  marsh  of  the  lagoon  shown  in  the  front  section  of  29  5  b  ? 
11.  Compare  in  29  5  b  and  5  c  the  breadth  of  the  reef ;  the  distance 
of  the  reef  (outside)  from  the  border  of  the  mainland ;  the  depth 
of  the  sea  at  n ;  at  q.  NOTE  :  The  depth  at  q  and  n  has  been  so 
much  increased  that  the  reef  front  is  now  attacked  by  the  waves, 
and  the  reef  retreats.  12.  WThy  does  some  of  the  reef  in  29  5  c  lie 
on  the  tide  marsh  ?  13.  In  some  cases  tide-marsh  mud  is  found  to 
"  outcrop  "  on  the  outer  beach  of  a  reef.  Draw  a  [red]  profile  in 
29  5  c  so  as  to  represent  this  condition.  Explain  it.  14.  As  the  re- 
treat of  the  reef  continues,  what  becomes  of  the  lagoon  ?  15.  Ex- 
plain 29  5  d. 

22.  1.  Which  part  of  the  coastal  plain,  29  6,  has  the  strongest 
seaward  slope  ?  the  weakest  seaward  slope  ?  2.  Has  an  offshore 
sand  reef  been  built  opposite  the  part  of  stronger  or  of  weaker 
slope  ?  3.  Which  part  of  the  plain  has  been  cut  back  in  a  low 
sea  cliff  ?  4.  Why  has  a  reef  been  formed  along  one  part  of  the 
shore  line  while  a  cliff  has  been  cut  along  a  neighboring  part  ? 


SHORE   LIXES  111 

5.  Where    has    most   of   the   material    for   the  reef  come    from  ? 

6.  Describe  the  change  along  the  shore  from  the  reef  to  the  cliff. 
Explain  it.    7.  Why  does  the  reef  bend  outward  at  a  certain  point  ? 
8.  Where  is  the  reef  interrupted  by  a  tidal  inlet  ?    9.  On  which 
side  of  the  inlet  is  the  reef  set  off  (or  offset)  farther  from  the  main- 
land ?     10.    From  which  direction  does  the  prevalent   longshore 
current  come  (see  broken-line  arrows)  ?     11.  Make  a  rule,  showing 
the  relation  between  the  offset  of  a  sand  reef  at  an  inlet  and  the 
direction  of  the  prevalent  longshore  current.    12.  Which  has  the 
smoother  outline,  the  outside  or  the  inside  of  a  sand  reef?    Why  ? 
[13.  At  times  of  heavy  storm  the  waves  may  wash  over  the  reef  at 
certain  points  ;  the  sand  thus  carried  into  the  lagoon  forms  what 
maybe  called  a  hurricane  delta.    14.  Where  does  such  a  delta  occur 
in  29  6  ?    Compare  its  position  with  that  of  one  of  the  small  stream- 
made  deltas.]    15.  The  sand,  drifted  along  the  beach  reef,  is  swept 
at  each  inlet  somewhat  offshore  by  the  ebb  tide,  and  is  carried  into 
the  lagoon  by  the  flood  tide.     Why  may  such  deposits  be  spoken 
of  as  tidal  deltas?    16.  Why  is  the  tidal  current  stronger  in  the 
inlets  than  elsewhere  ?    17.  What  effect  will  the  strong  tidal  current 
have  on  the  depth  of  the  inlet  ?    NOTE  :  The  outer  tidal  delta  is 
commonly  called  a  bar.     18.  How  will  the  depth  of  water  on  a  bar 
at  high  tide  affect  the  trade  and  growth  of  a  village  on  the  main- 
land shore  of  a  neighboring  lagoon  ?   [19.  A  large  part  of  the  coast 
line  of  the  Atlantic  and  Gulf  coastal  plain  in  the  southeastern 
United  States  is  fronted  by  sand  reefs,  broken  by  relatively  shallow 
inlets.    20.  What  effect  will  this  have  on  the  growth  of  commercial 
cities  along  the  coast?    21.  In  southern  Texas  a  sand  reef  incloses 
a  lagoon  for  90  mi.  without  a  break.   What  effect  will  this  have  on 
the  growth  of  cities  on  that  part  of  the  coast  ?] 

23.  1.  To  what  part  of  29  6  does  29  7  correspond  ?  Compare  29  6 
and  7  as  to  number  of  rivers  and  branches ;  as  to  fall  of  river  D  in 
feet  per  mile  ;  as  to  prominence  of  the  main  river  delta ;  as  to  area 
of  tide  marsh  and  lagoon  ;  as  to  position  of  tidal  inlet  (measure 
distance  alongshore  from  W.  border) ;  as  to  reef  offset  at  the  inlet ; 


112  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

as  to  length  of  cliffed  shore  line.  2.  Explain  the  changes.  3.  Sup- 
pose that  the  cliffed  shore  continues  to  retreat  in  29  7,  that  the 
main  delta  continues  to  grow  outward,  and  that  the  reef  near  the 
W.  border  of  the  figure  is  now  retreating  (see  29  5  c).  Draw  a 
[blue]  line  in  29  7  to  show  the  shore  line  thus  changed  (£"  or  £" 
retreat  at  each  end  of  shore  line)  ;  another  [blue]  line  to  show  a 
later  change  (in  this  line  let  the  delta  front  be  worn  a  little  back)  ; 
a  third  [blue]  line  to  show  a  still  later  change  (the  whole  shore 
line  retreating).  4.  On  the  third  line  is  any  of  the  original  shore 
line  of  the  coastal  plain  preserved  ?  Where,  and  why  ?  5.  What 
fraction  of  the  total  shore-line  length  is  then  cliffed  ?  In  what 
stage  of  development  is  the  shore  line  so  drawn  ?  [6.  Examine 
the  E.  branches  of  river  D.  Where  is  their  fall  most  rapid  ?  Why  ? 

7.  Draw  a  [red]  line  connecting  these  parts  of  most  rapid  fall. 
W7hat  may  such  a  line  be  called  ?    (See  Exercise  III,  §  5.)    8.  If 
29  7  showed  as  much  of  the  coastal  plain  as  29  6,  what  would  be  the 
general  position  of  the  fall  line  with  respect  to  the  coastal  plain  ? 
to  the  oldland  ?    9.  What  peculiar  feature  appears  in  the  oldland 
valleys  of  29  7  ?    Explain  it.    10.  Why  may  that  part  of  the  district 
be  described  as  having  "  young  valleys  in  the  bottom  of  its  older 
valleys  "  ?    11.  Draw  a  cross  profile  of  these  valleys.] 

24.  1.  By  what  process  has  29  7  been  transformed  in  29  8  ? 
2.  What  amount  of  regional  movement  has  occurred  ?  3.  Does  the 
movement  appear  to  have  been  uniform  or  of  unlike  amount  in 
different  parts  ?  4.  Did  the  movement  begin  immediately  after 
the  stage  reached  in  29  7  ?  How  can  you  tell  ?  5.  In  what  stage  of 
erosion  was  the  coastal  plain  when  the  movement  began  ?  6.  Does 
29  8  represent  a  stage  immediately  after  the  movement  ceased,  or 
has  some  time  passed  since  the  movement  ended  ?  How  can  you 
tell  ?  7.  Draw  a  [red]  line  to  show  the  shore  line  of  29  8  as  it 
was  when  the  movement  ceased.  How  does  that  shore  line  differ 
from  the  shore  line  printed  in  29  8  ?  8.  Why  are  some  of  the  bays 
longer  than  others  ?  Why  do  the  bays  branch  ?  9.  In  27  1,  29  6  and 

8,  which  one  has  a-  shore  line  of  (lancT)  elevation  ?  a  shore  line  of 


SHORE   LINES  113 

(land)  depression?  10.  Which  one  has  a  simpler  outline,  a  shore 
line  of  elevation  or  a  shore  line  of  depression  ?  Why  ?  11.  About 
how  high  are  the  little  cliffs  of  29  8  ?  12.  How  many  bays  (lagoons) 
are  entirely  inclosed  by  sand  reefs?  partly  inclosed?  13.  Which 
bays  have  fresh  water  ?  salt  water  ?  Why  ?  14.  Locate  a  city  in 
29  8  so  that  it  shall  have  a  good  harbor  for  ocean-going  vessels  and 
a  convenient  relation  to  the  interior  country.  Explain  the  advan- 
tages of  the  point  you  select.  15.  What  is  the  present  stage  of 
shore-line  development  in  29  8  ?  16.  Draw  a  [blue]  line  in  29  8 
to  show  the  shore  line  in  a  later  stage  of  development  (retreat 
of  J-^  mile).  17.  Draw  a  [red]  line  to  show  the  fall  line  of  298. 
18.  Which  parts  of  the  streams  may  be  called  revived?  [19.  I.n 
what  part  of  what  state  is  the  district  shown  in  27  1  a  ?  20.  With 
which  diagram  in  this  exercise  does  it  best  correspond  ?  21.  How 
many  partial  cycles  of  erosion  are  represented  ?  (Remember  that 
a  movement  of  elevation  or  depression  interrupts  the  preceding 
cycle  at  whatever  stage  it  has  reached,  and  introduces  a  new  cycle.) 

22.  In  what  stage  was  the  earlier  cycle  when  it  was  interrupted  ? 

23.  Was   it  interrupted  by  a  land  movement  of  elevation  or  of 
depression  ?    24.  What  has  happened  since  the  new  cycle  was  intro- 
duced ?    What  stage  has  it  now  reached  ?    25.  Draw  a  [red]  line 
to  show  the  shore  line  at  the  beginning  of  the  new  cycle.     About 
how  far  have  the  shore  cliffs  retreated  ?    26.  In  what  part  of  what 
state  is  27  2  e  ?   (It  lies  about  80  mi.  EXE.  of  35 1.)    27.  How  high  is 
the  shore  cliff  ?   In  what  stage  of  development  is  the  shore  line  ? 

28.  In  what  stage  of  development  is  the  lacustrine  coastal  plain  ? 

29.  In  what  stage  is  the  stream  near  the  left  end  of  the  map  ? 

30.  Do  the  stages  of  development  of  the  plain,  the  stream  and 
valley,  and  the  shore  line  agree  or  differ?    Explain.    31.  What  op- 
portunity for  harborage  is  offered  by  such  a  shore  line  ?]    [32.  Com- 
pare the  first  picture  on  the  next  page  with  the  picture  on  page  17. 
In  which  case  has  the  region  recently  been  elevated  ?   in  which,  de- 
pressed ?   How  can  you  tell  ?    33.  With  Avhich  map  of  this  exercise 
may  the  second  picture  on  the  next  page  be  compared  ?] 


114 


EXERCISES  IN  PHYSICAL  GEOGRAPHY 


25.  1.  Define  :  §  3,  rivers  dismembered  by  submergence,  embayed 
coast,  half-drowned  district ;  §  5,  sea  cliff,  initial  shore  line,  rock 
beach,  high  tide,  low  tide,  tidal  range,  sea  cave,  rock  arch,  cove, 
chasm,  stack,  skerry,  young  shore  line  ;  §  6,  beach ;  §  7,  barrier 
beach,  sand  reef;  §  8,  tidal  inlet,  flood  tide,  ebb  tide,  lagoon,  tide 
marsh ;  §  9,  spit,  hooked  spit,  initial  (or  original)  shore  line,  young 
shore  line,  early  mature  shore  line,  fully  mature  shore  line  ;  §  11, 
land- tied  island  remnant;  [§  12,  delta-tied  island,  delta-inclosed 
lakes;]  §  17,  streams  betrunked  by  cliff  retreat;  §  20,  rivers  ex- 
tended by  emergence,  rivers  engrafted  by  emergence,  elevated 
sea  cliffs ;  [§  22,  hurricane  delta ;]  §  24,  shore  line  of  elevation, 
shore  line  of  depression. 


EXERCISE  X.    THE  DISTRIBUTION  OF  TEMPERATURE 

OBJECT.  To  learn  the  distribution  of  temperature  over  the  world  and 
its  changes  with  the  seasons. 

Preliminary.  This  exercise  treats  of  the  temperature  of  the  lower 
air,  near  the  surface  of  the  land  or  sea.  The  temperature  of  the 
air  is  determined  by  the  thermometer,  placed  where  it  is  open  to 
the  wind  but  sheltered  from  sunshine  and  rain.  The  Fahrenheit 
scale  is  here  used.  Observations  of  temperature  have  been  regu- 
larly taken,  day  after  day,  in  many  parts  of  the  world  for  many 
years,  and  the  results  have  been  charted,  as  explained  below;  so 
that  the  distribution  of  temperature  is  easily  studied  by  means  of 
maps.  This  exercise  uses  Plates  30  and  31. 

1.  1.  The  figures  in  30 1  are  records  of  temperature,  such  as 
might  be  determined  by  observations  taken  at  the  same  hour  in 
various  parts  of  the  central  United  States.  In  what  states  there 
shown  do  temperatures  higher  than  60°  prevail  at  this  time  ?  tem- 
peratures lower  than  10°  ?  2.  Complete  the  line  separating  the  part 
of  the  map  where  the  temperature  is  over  40°  from  the  part  where 
the  temperature  is  under  40°.  What  is  the  temperature  of  places  on 
this  line  ?  NOTE  :  Such  a  line  is  called  a  line  of  equal  temperature, 
or  isotherm.  3.  Print  40°  at  each  end  of  the  isotherm.  4.  Draw 
the  isotherms  for  50°,  60° ;  for  30°,  20°,  10°,  0°.  Print  the  proper 
numbers  at  each  end  of  these  isotherms.  5.  Why  is  the  distribution 
of  temperature  more  clearly  shown  by  the  isotherms  than  by.  the 
separate  observations  ?  6.  Draw  a  line  from  SE.  Texas  across  the 
map,  to  show  the  path  you  would  follow  in  order  to  find  the  most 
rapid  decrease  of  temperature  ;  draw  similar  lines  from  S.  Illinois  ; 
from  SW.  Tennessee.  7.  Are  these  lines  parallel  ?  Are  they  straight? 
8.  What  is  the  relative  direction  of  the  lines  of  temperature  decrease, 

115 


116  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

or  lines  of  temperature  gradient,  and  the  isotherms  ?  9.  In  what 
part  of  what  state  is  the  most  rapid  decrease  of  temperature,  or 
the  strongest  temperature  gradient,  found?  10.  In  what  part  of 
the  map  is  the  decrease  of  temperature  least  rapid,  or  the  tempera- 
ture gradient  weakest  ?  11.  How  is  the  strength  or  weakness  of  the 
temperature  gradient  indicated  by  the  spacing  of  the  isotherms  ? 

12.  How  much  stronger  is  the  temperature  gradient  in  E.  Kansas 
than  in  Arkansas  ?   How  can  you  tell  ?    13.  Draw  three  more  tem- 
perature gradient  lines  across  the  map.    What  is  their  general  direc- 
tion ?    14.  If  temperatures  remain  as  in  30  1,  in  what  directions 
might  one  travel  from  SW.  Missouri  to  find  no  change  of  tempera- 
ture ?    Would  the  path  of  travel  be  straight  or  curved  ? 

2.  1.  What  is  meant  by  the  mean  annual  temperature  of  a 
place  ?  (DE,  34.7.)  How  is  it  determined  ?  2.  What  does  30  2 
show  ?  3.  Shade  lightly  [red]  all  the  space  in  so  2  where  the 
mean  annual  temperature  is  over  70° ;  [blue]  under  30°.  4.  Print 
ArCtic  Cold  Cap,  N.  Temperate  Belt,  Torrid  Belt,  S.  Temperate 
Belt,  AntarCtic  Cold  Cap  on  the  five  belts  indicated  by  the  shading 
and  blank  spaces  on  30  2.  5.  Why  are  two  of  these  spaces  called 
"  caps,"  and  the  other  three  "  belts  "  ?  6.  What  countries  of  N.  and 
S.  America  are  in  the  several  belts?  of  Europe  and  Africa?  of  Asia 
and  Australia?  7.  Which  grand  division  of  land  (N.  America,  S. 
America,  Europe,  Asia,  etc.)  has  the  largest  area  in  the  Arctic  cold 
cap  ?  in  the  torrid  belt  ?  8.  In  what  belt  is  your  school  ?  9.  Draw 
a  [blue]  line  along  the  isotherm  of  50°  in  each  hemisphere.  In 
which  belt  is  the  50°  isotherm  more  regular  ?  10.  Draw  lines  to 
show  parallels  of  latitude  60°  N.  and  S.  (nearly  halfway  from  the 
parallel  of  40°  to  that  of  80°).  11.  Estimate  the  successive  highest 
and  lowest  temperatures  through  which  these  lines  pass.  Print  the 
figures  indicating  these  temperatures  in  their  proper  places.  12.  On 
which  of  these  lines  is  the  greatest  temperature  variation  found  ? 

13.  Shade  with  vertical  lines  the  areas  of  more  than  80°  mean  annual 
temperature.    14.  Do  these  areas  lie  chiefly  on  land  or  on  water  ? 
15.  Shade  in  the  same  way  the  area  of  less  than  10°.    16.  Does  it 


117 

extend  farther  toward  the  equator  on  land  or  on  water  ?  17.  Is  the 
poleward  decrease  of  temperature  (poleward  temperature  gradient) 
in  the  N.  temperate  belt  stronger  on  Asia  or  on  the  N.  Atlantic? 
on  the  N.  Pacific  or  on  1ST.  America  ?  on  northern  continents  or  on 
northern  oceans  ? 

3.  1.  What  do  31 1  and  2  show  ?    2.  On  these  maps  shade  the 
areas  under  30°  [light  blue]  and  over  70°  [light  red] ;  shade  more 
heavily  the  areas  under  0°  and  over  80°.     3.  Where  are  the  hot 
regions  (monthly  mean  over  80°)  in  January  ?  in  July  ?    4.  Where 
are  the  very  cold  regions  (monthly  mean  under  0°)  in  January  ?  in 
July  ?    5.  In  what  month  have  the  hot  regions  the  greatest  area  ? 
the  cold  regions  the  greatest  area  ?    Why  ?    (DE,  52.2  ;  G,  245.3  ; 
T,  238.2.)    6.  In  what  direction  from  your  school  is  the  nearest 
cold  region  in  January  ?  the  nearest  hot  region  in  July  ?    7.  Draw 
on  31 1  and  2  lines  of  temperature  gradient  through  your  school  for 
January  and  July.    What  are  the  directions  of  these  lines  ?    NOTE  : 
If  the  temperature  maps  extended  farther  south,  a  region  of  great 
cold  would  be  shown  near  the  South  Pole  in  July.    8.  In  what 
parts  of  the  world  and  in  what  month  do  the  hot  regions  extend 
farthest  from  the  equator  ?  the  very  cold  regions  farthest  towards 
the  equator  ?    Why  ? 

4.  1.  Make  a  mark  across  each  meridian  in  31 1  where  the  high- 
est temperature  occurs.     2.  How  do  you  determine  where  to  place 
these  marks  ?   3.  Draw  several  N.-S.  lines  across  the  areas  of  over 
80°  (or  90°)  ;  place  marks  at  the  middle  points  of  these  lines.    Draw 
a  curved  line  through  all  the  marks.    4.  Why  may  this  curve  be 
called  the  heat  equator  for  January  ?    5.  Estimate  the  highest  and 
lowest  temperatures  found  on  the  January  heat  equator,  and  print 
their  values  in  31 1.    6.  Draw  in  31  2  the  heat  equator  for  July  in 
the  same  way.    7.  Copy  the  July  heat  equator  (dotted  line)  on 
31 1 ;  shade  with  light  vertical  lines  the  belt  between  the  two  posi- 
tions of  the  heat  equator.    What  descriptive  name  can  be  given  to 
the  belt  thus  shaded  ?    (Use  the  terms  migration,  heat  equator,  and 
annual  in  your  answer.)     [8.  Mark  a  strong  [red]  N.-S.  line  where 


118  EXERCISES  IN  PHYSICAL   GEOGRAPHY 

the  heat  equator  migrates  from  the  geographic  equator  to  30°  X. 
lat. ;  another  where  the  migration  is  from  20°  N.  lat.  to  20°  S.  lat.  ; 
from  15°  K  to  20°  S.;  from  10°  N.  to  25°  N.;  from  5°  S.  to  40°  N. ; 
from  0°  to  20°  S.  ;  from  5°  S.  to  15°  S.]  9.  Where  is  the  migration 
of  the  heat  equator  of  large  value  and  about  the  same  N.  and  S.  of 
the  geographic  equator  ?  Why  ?  10.  Where  is  the  greatest  northern 
migration?  Why?  11.  Where  does  the  belt  of  migration  remain 
N.  of  the  equator  all  the  year  (DP,  40.4,  40.9)  ?  S.  of  the  equator 
all  the  year?  Why?  12.  Does  the  heat  equator  migrate  farther 
from  the  geographic  equator  on  the  continents  or  on  the  oceans  ? 
Why  ?  13.  Is  the  belt  of  migration  wider  on  the  continents  or  on 
the  oceans?  Why?  [14.  Does  the  apparent  annual  migration  of  the 
sun  carry  it  the  same  distance  N.  and  S.  of  the  geographic  equator? 
How  do  you  know  ?  15.  Is  the  annual  migration  of  the  heat  equa- 
tor symmetrical  ?  16.  Why  do  the  two  not  agree  ?] 

5.  1.  During  what  months  is  the  heat  equator  migrating  north- 
ward ?     2.  What  general  changes  of  temperature  take  place  in  the 
N.   hemisphere    during   these   months  ?    in   the    S.    hemisphere  ? 
3.  What  changes  take  place  in  these  months  in  the  slant  of  the 
sun's  rays  in  the  N.  hemisphere  ?   in  the  S.  hemisphere  ?    4.  What 
changes  take  place' during  the  same  months  in  the  length  of  the 
days  and  nighta  in  the  N.  hemisphere  ?    in  the  S.  hemisphere  ? 
(DE,  48.8-,  87.1-  ;  DP,  400.1-  ;  G,  21.3-  ;  T,  400-.)  5.  During  what 
months  does  the  heat  equator  migrate  southward?   Why?    6.  What 
general  changes  in  temperature  are  taking  place  in  the  two  hemi- 
spheres during  these  months?   Why?    7.  Copy  on  31 1  the  isotherms 
of  40°  from  both  hemispheres  of  31  2.    Shade  with  light  vertical 
lines  the  belts  thus  indicated.     8.  What  names   may  be  given  to 
these  belts  ?     9.  Which  is  the  wider  and  more  irregular  belt  ?     Is 
it  wider  on  the  continents  or  on  the  oceans?    Why?    10.  Where  is 
your  school  located  with  respect  to  one  of  these  belts  ? 

6.  [1.  Draw  a  meridian  from  top  to  bottom  of  31 1  in  20°  W.  long. 
Lay   a   strip   of   paper   along   the   meridian  ;    mark  on   the  edge 
of  the  strip  where  the  equator  and  the  successive  isotherms  are 


THE   DISTRIBUTION  OF  TEMPERATURE  119 

crossed  ;  print  the  values  of  the  isotherms  near  their  marks. 
2.  Place  the  strip  along  any  horizontal  line  in  30  4  a,  with  north  to 
right  and  the  equator  mark  at  EQK.  Transfer  the  isotherm  marks 
to  the  horizontal  line,  and  indicate  their  values.  3.  Make  dots  in 
30  4  a  at  points  above  or  below  the  transferred  isotherm  marks,  so 
as  to  represent  the  value  of  the  isotherms  on  the  vertical  tempera- 
ture scale  of  30  4  a.  Draw  a  curve  through  the  dots.  4.  Draw  a 
corresponding  curve  for  July  in  so 4  a.  5.  Print  JANUARY  on  one 
curve  and  JULY  on  the  other.  6.  What  do  these  curves  represent? 
7.  How  is  the  migration  of  the  heat  equator  indicated  by  the  two 
curves  ?  8.  Draw  vertical  lines  in  the  space  between  the  two 
curves.  What  do  these  lines  represent?  9.  About  how  much  does 
the  air  temperature  over  the  Atlantic  change  between  January  and 
July  in  the  torrid  belt?  in  the  N.  temperate  belt  ?  in  the  S.  temper- 
ate belt  ?  10.  Draw  a  meridian  line  of  20°  E.  long,  from  the  S. 
border  of  31 1  to  the  S.  point  of  Africa  ;  continue  the  line  a  little 
E.  of  N.  to  central  Arabia  ;  then  NE.  (through  the  small  oval  iso- 
therm of  —60°)  to  the  Arctic  ocean,  and  thence  N.  to  the  N.  border 
of  the  map.  11.  Mark  EQ  on  the  middle  of  a  strip  of  paper;  lay 
the  strip  on  31 1,  keeping  EQ  on  the  equator  and  moving  the  strip 
parallel  to  the  meridians  ;  mark  on  the  strip  the  points  where  the 
successive  isotherms  cross  the  line  just  drawn  through  Africa  and 
Asia ;  indicate  on  the  strip  the  values  of  the  isotherms.  12.  Trans- 
fer, as  before,  the  isotherm  marks  to  31  4  b,  and  draw  the  January 
curve.  13.  Do  the  same  for  July.  14.  Print  JANUARY  and  JULY 
on  the  curves.  What  do  they  represent  ?  15.  How  do  they  differ 
from  the  curves  of  31  4  a  as  to  the  temperature  of  the  heat  equator  ? 
as  to  the  migration  of  the  heat  equator  ?  as  to  temperatures  in  far 
S.  latitudes  ?  in  far  N.  latitudes  ?  16.  What  difference  is  shown 
by  the  two  pairs  of  curves  as  to  January-July  temperature  range 
in  the  N.  hemisphere?  in  the  S.  hemisphere?  17.  Why  are 
these  ranges  greater  in  NE.  Asia  (31  4  i)  than  in  the  N.  Atlantic 
(31  4  a)  ?  18.  Draw  vertical  lines  between  the  two  curves  of  31  4 1. 
What  do  they  represent  ?  19.  Mark  arrowheads  on  the  January  end 


120  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

of  the  vertical  lines.    Why  do  some  of  the  arrows  point  upwards, 
some  downwards  ?] 

7.  [NOTE  :  Let  the  mean  annual  temperature  range,   or  differ- 
ence between  the  means  of  the  warmest  and  coolest  months  (not 
necessarily  January  or  July  near  the  equator)  for  many  places  be 
entered  on  a  map  of  the  world  ;  let  lines  be  drawn  through  points 
having  equal  annual  range.    Such  lines  are  shown  in  30.3.     1.  What 
name  may  be  given  to  this  map  ?     NOTE  :    Temperatures  in  far 
southern  latitudes  are  not  well  known,  but  as  far  as  60°  S.  the 
annual  range  over  the  oceans  is  probably  less  than  20°.     2.  Shade 
in  30  3  with  dots  the  regions  of  less  than  20°  annual  range.    3.  Shade 
lightly  with  vertical  lines  the  regions  of  more  than  30°  range  ; 
shade  more  heavily  the  regions  of  more  than  60°  range.    4.  In  what 
general  parts  of  the  world  is  the  annual  range  of  temperature  small 
(under  20°)  ?    large  (over  60°)  ?     5_  How  is  your  school  situated 
with  respect  to  any  one  of  these  regions  ?     6.  How  are  the  charac- 
teristics of  oceanic  and  of  continental  climates  illustrated  in  30  3  ? 
(DE,   50.7;    DP,  41.6;    T,   277.3.)     7.  Draw   several  temperature 
gradient  lines  in  different  parts  of  30  2  ;  mark  arrowheads  on  the 
lines  to  show  the  direction  of  temperature  decrease.    8.  What  is 
the  usual  direction  of  temperature  gradient  lines  in  the  N.  hemi- 
sphere ?    in  the  S.  hemisphere  ?    9.  What  is  the  direction  of  the 
January  temperature  gradient  line  (see  31 1)  in  Baffin  bay  (between 
Labrador  and  Greenland)  ?   at  North  cape  (N.  point  of  Norway)  ? 
on  NE.  coast  of  Asia?    10.  What  is  the  direction  of  the  July  tem- 
perature gradient  line  (see  31  2)  in  S.  California  ?    in  SE.  Arabia  ? 
11.  State  the  cause  of  the  unusual  direction  of  the  temperature 
gradient  lines  indicated  in  questions  9  and  10.] 

8.  Define  :   §  1,  line  of  temperature  gradient ;  §  4,  heat  equator  ; 
[§  7,  mean  annual  temperature  range.] 


EXEECISE  XI.    THE  PEEV AILING  WINDS  OF  THE 

WORLD 

OBJECT.  To  learn  the  prevailing  winds  of  various  parts  of  the  world, 
their  changes  with  the  seasons,  and  the  control  that  they  exert  over  the 
distribution  of  rainfall  in  different  regions  and  in  different  seasons  of 
the  year. 

Preliminary.  The  prevailing  winds  for  January  and  July  are 
charted  in  32  1  and  2,  as  determined  by  observations  made  in  many 
different  parts  of  the  world  on  land  and  at  sea.  Winds  are  given 
the  name  of  the  direction  from  which  they  blow.  The  arrows  on 
the  charts  fly  with  the  winds:  the  heavier  the  arrow,  the  greater  the 
average  strength  of  the  wind  ;  the  longer  the  arrow,  the  steadier 
the  wind.  Little  circles  indicate  light  variable  winds  with  frequent 
calms.  Windward  means  the  direction  from  which  the  wind  is 
blowing  ;  leeward  means  the  direction  toward  which  the  wind  is 
blowing.  The  winds  are  stronger  and  more  regular  over  the  oceans 
than  over  the  lands,  where  mountains  and  valleys  affect  their 
velocity  and  direction.  Many  of  the  following  questions  refer 
chiefly  to  the  winds  of  the  oceans.  This  exercise  uses  32  1  and  2, 
34  3  and  4. 

1.  1.  Examine  the  winds  of  the  Atlantic  ocean  in  32l.  Print 
SW  about  the  middle  of  the  region  where  SW.  winds  prevail ; 
NE,  SE,  NW,  where  corresponding  winds  prevail.  2.  Draw  a  [blue] 
line  in  the  N.  Atlantic  separating  the  westerly  (NW.,  W.,  SW.) 
winds  from  the  easterly  (NE.,  E.,  SE.)  winds.  Prolong  the  line 
westward  through  the  Gulf  of  Mexico ;  eastward  across  N.  Africa 
and  S.  Asia.  (This  line  should  run  square  across  N.  or  S.  winds.) 
3.  Draw  a  [blue]  line  in  the  equatorial  Atlantic  separating  the 
northerly  (NE.,  N.,  NW.)  winds  from  the  southerly  (SE.,  S.,  SW.) 

121 


122  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

winds.    4.  Draw  a  line  in  the  S.  Atlantic  separating  the  easterly 
(SK,  E.,  NE.)  winds  from  the  westerly  (NAY.,  W.,  SW.)  winds. 

5.  Do  the  same  for  the  Pacific  ocean  (omit  the  W.  Pacific) ;  for  the 
Indian  ocean.     6.  Print  JAN.  on  the  boundary  lines  that  you  have 
thus  drawn  in  each  ocean.    7.  Connect  the  [blue]  lines  across  the 
continents  (omitting  E.  Asia),  following  the  rules  regarding  wind 
directions  already  given.    8.  Treat  32  2  in  the  same  way,  printing 
SW,    NE,  etc.,  in  the   several  wind  regions,  and   drawing   [blue] 
lines  separating  the  regions  of  unlike  winds.     9.  Print  JULY  on 
these  lines. 

2.  1.  Around  what  part  of  the  world,  limited  roughly  by  lati- 
tude circles,  do  NW.  (or  WNW.)  winds  prevail  in  January  and  July  ? 

2.  Why  may  this  part  of  the  world  be  spoken  of  as  a  wind  belt? 

3.  Between  what  latitudes  (roughly)  do  SE.  winds  for  the  most  part 
prevail?    NE.  winds  ?    SW.  (or  WSW.)  winds  ?    NOTE  :  Although 
the  winds  of  these  belts  are  somewhat  irregular  on  the  ocean  (for 
example,  the  SE.  wind  belt  in  the  W.  Pacific  for  January),  and 
are  more  or  less  interrupted  on  the  continents,  they  are  commonly 
spoken  of  as  if  they  extended  all  around  the  world.    4.  What  names 
are  ordinarily  given  to  the  several  wind  belts  ?    (DE,  39.5-  ;  DP, 
30.1-  ;  G,  258.3-  ;   T,  259.4-.)    5.  In  which  belts  are  the  winds  rela- 
tively steady  ?    In  which  belts  are  winds  less  steady  but  stronger  ? 

6.  Do  light  winds  and  frequent  calms   prevail  within  the  wind 
belts,  or  along  the  boundaries  between  them  ?    7.  How  many  such 
belts  of  light  winds  and  frequent  calms  are  indicated  ?    What  names 
are  given  to  them?    (DE,  43.4,  44.5  ;  DP,  32.5,  33.1;   G,  260.1-4  ; 
T,  259.2,  261.9.) 

3.  1.  In  which  ocean  are  the  westerly  winds  most  uniform?  Why? 
2.  In  which  northern  ocean  are  the  westerly  winds  most  deflected 
from  their  usual  WSW.  direction   in  January?    in  July?    3.  In 
which  ocean  are  the  trafle  winds  most  deflected  from  their  usual 
course  in  January  ?   in  July  ?    4.  Around  which  grand  division  of 
land  (Europe,  Asia,  Africa,  etc.)  are  the  prevailing  winds  in  July 
most  deflected  from  the  wind-belt  directions  ?    (Special  account  6f 


THE   PREVAILING  WINDS  OF  THE  WORLD  123 

these  deflected  winds  will  be  given  in  §§  8  and  9.)  5.  Which  wind 
belt  includes  the  greatest  part  of  the  United  States  ?  G.  On  which 
coast  (Atlantic  or  Pacific)  of  the  United  States  do  the  winds  there- 
fore blow  prevailingly  from  sea  to  land  ?  from  land  to  sea  ? 
7.  In  what  wind  belt  do  Mexico  and  Central  America  lie?  On 
which  coast  (northeast  or  southwest)  do  the  winds  there  prevail- 
ingly blow  from  sea  to  land  ?  from  land  to  sea  ?  8.  What  part 
of  S.  America  S.  of  the  equator  is  covered  by  a  belt  of  easterly 
winds  ?  of  westerly  winds  ?  9.  What  parts  of  the  coast  of  S.  Amer- 
ica S.  of  the  equator  have  winds  prevailingly  from  sea  to  land? 
from  land  to  sea  ?  10.  Answer  the  same  questions  for  Africa  S.  of 
the  equator.  11.  What  wind  belt  covers  the  greatest  part  of  Africa 
N.  of  the  equator  ?  of  Europe  ?  12.  Compare  the  E.  coast  of  N. 
America  (Florida  to  Labrador)  with  the  W.  coast  of  Europe  (Spain 
to  Norway),  as  to  prevalence  of  winds  from  land  or  from  sea. 

4.  1.  What  kind  of  weather  prevails  in  the  doldrums  at  sea  (DE, 
43.6;  DP,  32.6;   G,  260.1  ;   T,  279.9)?    in  the  trade-wind  belts  at 
sea  (DE,  40.7;   DP,  30.8,  52.7;  G,  259.8)?    in  the  horse  latitudes  at 
sea  (DE,  44.7;    DP,  33.2)?    in  the  belts  of  westerly  winds  at  sea 
(DE,  42.6 ;  DP,  31.9 ;   G,  258.7)  ?    2.  How  does  the  weather  in  the 
belt  of  westerly  winds  vary  from  winter  to  summer  ?    (DE,  54.8  ; 
DP,  36.7.)    3.  What  kind  of  weather  prevails  in  the  Pacific  ocean 
just  N.  of  the  equator,  140°  W.  long.?  in  the  torrid  Atlantic  where 
you  have  printed  NE  and  SE  ?  in  the  N.  and  S.  Atlantic  where  you 
have  printed  SW  and   NW  ?   4.  Would  rainfall  (rain  and  snow)  be 
more  plentiful  on  coasts  where  the  winds  usually  blow  from  sea  to 
land,  or  from  land  to  sea  ?    5.  Shade  [blue]  in  32  2  the  coasts  (omit 
E.  Asia  for  the  present)  in  the  belts  of  westerly  winds  where  plenti- 
ful rainfall  may  be  expected.    6.  In  what  countries  are  these  coasts  ? 
(Consult  maps  of  continent,  Plates  40-45,  if  necessary.) 

5.  1.  Would  rainfall  be  more  plentiful  from  winds  that  are  blow- 
ing (obliquely)  towards  the  pole,  and  therefore  cooling,  or  from 
winds  that  are  blowing  (obliquely)  towards  the  equator,  and  there- 
fore warming?   (DE,  40.4  ;  DP,  30.6.)    2.  Shade  with  [blue]  lines  the 


124  EXERCISES   IX  PHYSICAL  GEOGRAPHY 

coasts  where  the  trade  winds  blow  from  sea  to  land  (omit  N.  Africa  ) ; 
shade  with  [red]  dots  the  coasts  where  the  trade  winds  blow  from 
land  to  sea,  or  parallel  to  the  shore  line.  3.  Which  of  these  coasts 
would  have  plentiful  rainfall  ?  Which  would  be  dry  or  desert  ? 
4.  On  which  coast  of  Mexico  and  Central  America  would  you  expect 
the  heavier  rainfall  ?  Why  ?  5.  Why  is  the  W.  coast  of  SW.  Africa 
a  dry  region,  while  the  E.  coast  has  a  plentiful  rainfall  ?  6.  When 
moist  winds  blow  across  a  high  mountain  range,  ascending  its 
windward  slope  and  descending  its  leeward  slope,  which  slope  of 
the  range  will  be  rainy  ?  which  slope  dry  ?  (DE,  41.3  ;  DP,  31.2.) 
7.  Would  rainfall  be  plentiful  or  scanty  on  the  interior  lowlands 
to  the  leeward  of  such  a  range  ?  8.  Consult  the  maps,  Plates  40-45, 
and  32  1  and  2,  and  name  the  coasts  where  the  prevailing  winds 
encounter  mountains  as  they  blow  from  sea  to  land.  9.  What  can 
you  say  as  to  the  rainfall  of  E.  and  W.  Oregon  ?  of  California  and 
Nevada  ?  Explain.  10.  Describe  the  relation  of  the  Andes  to  the 
wind  belts  which  cross  these  mountains  ;  state  the  probable  distri- 
bution of  forests  on  the  slopes  of  the  Andes.  11.  In  what  countries 
(see  Plate  42)  would  the  W.  slope  of  the  Andes  be  dry  or  desert  ? 
12.  Compare  the  rainfall  in  different  parts  of  Peru  and  of  Patagonia, 
with  respect  to  the  Andes  and  the  prevailing  winds.  13.  What 
amount  of  rainfall  would  you  expect  on  the  mountainous  islands, 
Sumatra  and  Borneo,  between  Asia  and  Australia?  Explain.  14. 
On  which  slope  of  the  volcanic  mountains  of  the  Hawaiian 
islands  may  the  heavier  rainfall  be  expected  ?  15.  Where  trade 
winds  blow  across  nonmountainous  interior  regions  and  become 
warmer  as  they  advance,  would  you  expect  plentiful  or  scanty 
rainfall?  (DE,  41.1;  DP,  30.8;  G,  236.2;  T,  281.8.)  16.  Shade 
[red]  the  interior  parts  of  IS",  and  S.  Africa  and  of  Australia  that 
are  crossed  by  the  trade  winds  but  not  visited  by  the  doldrum  belt 
or  the  horse-latitude  belt.  Would  these  regions  be  forested  or 
desert?  17.  In  what  parts  of  each  continent  are  these  regions  ? 

6.    [1.  Copy  [blue]  on  32  1  the  boundary  lines  of  the  wind  belts 
(or  belts  of  frequent  calms)  from  322.    (Place  these  lines  carefully 


THE  PREVAILING  WINDS  OF   THE  WORLD  125 

with  respect  to  latitude  lines  and  to  points  on  the  coast.)  2.  Print 
JULY  on  the  copied  lines.  3.  About  what  change  of  latitude  takes 
place  in  the  position  of  the  boundaries  of  the  wind  belts  (omit  the 
Indian  and  W.  Pacific  ocean)  from  January  to  July  ?  from  July  to 
January?  4.  How  does  this  change  correspond  with  the  change  in 
the  position  of  the  sun  in  the  sky  for  the  same  periods  ?  5.  How 
does  the  amount  of  change  compare  in  the  two  cases  ?  6.  Compare 
the  position  of  the  doldrums  in  January  and  July  with  the  position 
of  the  heat  equator,  31 1  and  2,  for  the  same  months.  7.  What  seems 
to  be  the  relation  of  the  doldrums  and  the  trade  winds  to  the  heat 
equator  ?  NOTE  :  The  heat  equator  in  January  and  July  is  a  better 
indication  of  the  position  of  the  doldrums  on  the  lands  in  those 
months  than  is  given  by  the  winds  of  32  1  and  2.  8.  Copy  on  32  1 
the  heat  equator  of  Africa  and  S.  America,  31 1  and  2;  print 
JAN.  and  JULY  on  the  copied  lines,  and  let  the  migration  of  the 
doldrums  on  those  continents  be  thus  defined.  9.  Shade  with  light 
vertical  [blue]  lines  in  32 1  the  belt  across  which  the  doldrums 
migrate.  This  belt  may  be  called  the  subequatorial  belt.  10.  Shade 
in  32 1' the  belts  across  which  the  calms  of  the  horse  latitudes 
migrate.  These  belts  may  be  called  the  N.  and  S.  subtropical  belts.'] 
7.  If  §  6  is  omitted,  omit  §  7  also.  [1.  What  sort  of  weather  will 
prevail  at  a  place  on  the  N.  side  of  the  subequatorial  belt  in  Jan- 
uary ?  in  July  ?  2.  What  sort  of  weather  at  a  place  on  the  S.  side 
of  the  same  belt  in  January  ?  in  July  ?  3.  What  sort  of  weather 
at  a  place  in  the  middle  of  the  same  belt  in  January  ?  in  April  ?  in 
July  ?  in  October  ?  4.  Draw  a  line  around  the  area  drained  by  the 
river  Nile  in  Plate  45  ;  shade  lightly  the  river  basin  thus  inclosed. 
Do  the  same  for  the  Zambezi  river  in  S.  Africa.  5.  In  which  month, 
January  or  July,  will  you  expect  high  water  'in  the  Nile  ?  in  the 
Zambezi  ?  Explain.  (See  the  migration  of  the  doldruin  belt  in 
Africa,  32  1.)  6.  In  what  parts  of  Africa  would  you  expect  to  find 
deserts  ?  grass  and  trees  ?  dense  forests  ?  NOTE  :  The  heavier 
the  rainfall  of  warm  regions,  the  denser  the  tree  growth.  7.  The 
plains  of  the  interior  of  Venezuela,  lat.  5°  N.,  have  abundant  rains 


126  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

in  July  and  August,  but  are  dry  in  the  opposite  season ;  the  plains 
of  the  interior  of  Brazil,  lat.  10°  S.,  have  abundant  rains  from  Decem- 
ber to  February,  but  are  dry  in  the  opposite  season.  Locate  these 
plains  on  Plate  42,  and  account  for  their  rainy  and  dry  seasons. 
8.  Bogota  (locate  on  Plate  42)  has  abundant  rainfall  in  April  and 
May  and  in  October  and  November,  and  a  less  rainfall  in  the  other 
months.  Account  for  these  variations.  9.  What  sort  of  weather  will 
prevail  at  a  place  in  the  N.  subtropical  belt  in  January  ?  in  July  ? 
10.  What  sort  of  weather  will  prevail  in  the  S.  subtropical  belt 
in  January?  in  July?  Explain.  11.  In  what  months  w6uld  you 
expect  the  rainy  season  in  S.  California  ?  in  Morocco  and  Algiers  ? 
Locate  the  last  two  countries  on  Plate  45.  12.  In  what  months 
would  you  expect  the  rainy  season  in  Chile,  lat.  30°  S.  ?  in  Cape 
Town,  S.  Africa?  in  S.  Australia?  in  N.  Australia?] 

8.  NOTE  :  The  prevailing  winds  of  the  Indian  ocean  for  Jan- 
uary and  July  are  shown  in  34  3  and  4  on  a  larger  scale  than  in  32  1 
and  2.  1.  In  which  month  do  the  NE.  trades  of  the  Indian  ocean 
seem  to  extend  across  the  equator  ?  2.  Why  do  they  not  stop  at  the 
equator  ?  3.  What  direction  do  they  take  after  crossing  the  equator  ? 
4.  Shade  lightly  the  space  occupied  by  these  extended  and  deflected 
trade  winds  in  34  3.  5.  What  is  the  direction  of  the  winds  in  this 
region  in  July  ?  (See  34  4.)  6.  What  name  is  given  to  winds  that 
thus  reverse  their  directions  in  the  opposite  seasons  ?  (DE,  57.1  ; 
DP,  43.5  ;  G,  262.1  ;  T,  256.9.)  7.  In  which  month  do  the  SE. 
trades  of  the  Indian  ocean  seem  to  cross  the  equator  ?  8.  What 
direction  do  they  take  after  crossing  the  equator  ?  9.  To  about 
what  latitude  are  they  then  continued  ?  10.  AVhy  do  they  go  farther 
N.  than  the  extended  NE.  trades  go  S.  of  the  equator  ?  11.  Shade 
the  region  of  the  extended  SE.  trades  in  34  4.  12.  What  is  the  direc- 
tion of  the  prevailing  winds  in  this  region  in  January  ?  (See  34 3.) 
13.  What  two  regions  of  monsoon  winds  are  thus  shown  in  the 
Indian  ocean  (and  S.  Asia)  ?  14.  How  are  they  situated  with 
respect  to  the  equator?  15.  Which  one  is  the  larger?  16.  What 
is  the  relation  of  the  heat  equator  to  these  monsoon  regions  ? 


THE   PREVAILING   WINDS  OF  THE  WORLD  127 

[17.  Where  else  than  in  the  Indian  ocean  do  the  NE.  trades  seem  to 
cross  the  equator  in  January  and  extend  into  the  S.  hemisphere  ? 
(See  32 1.)  18.  What  is  the  direction  of  the  winds  between  the 
equator  and  Australia  in  January  ?  in  July  ?  19.  Why  may  these 
winds  be  called  the  Australian  monsoons  ?  20.  Shade  [red]  on  322 
the  region  of  these  monsoons.  21.  Where,  besides  in  the  Indian 
ocean,  do  the  SE.  trades  seem  to  cross  the  equator  in  July  and  ex- 
tend into  the  N.  hemisphere  ?  (See  32  2.)  22.  In  what  small  regions 
do  these  extended  winds  show  a  deflection  from  SE.  to  SW.  ?  23. 
What  is  the  direction  of  the  January  winds  in  these  regions  ?  24. 
What  name  m'ay  be  given  to  the  winds  of  these  small  regions  ? 
25.  Shade  [red]  these  regions  in  32  2.  NOTE  :  It  is  probable  that 
winds  resembling  monsoons,  but  less  regular  and  less  steady  than 
the  monsoons  of  the  Indian  ocean,  occur  in  torrid  Africa  and  S. 
America.  2G.  How  many  monsoon  regions  of  this  kind  may  be 
expected  on  these  continents  ?  27.  Draw  in  32  2  two  arrows  in  each 
of  these  monsoon  regions,  to  show  the  expected  wind  directions  in 
January  [blue]  and  in  July  [red].] 

9.  1.  In  what  month  does  the  heat  equator  advance  upon  S.  Asia? 
2.  Compare  the  displacement  of  the  heat  equator  from  the  geo- 
graphic equator,  as  there  shown,  with  the  displacement  in  other 
parts  of  the  world.  3.  In  what  month  does  the  air  over  Asia  become 
warmer  than  the  air  over  the  oceans  on  the  SE.  and  N.?  colder 
than  the  air  over  the  same  oceans  ?  4.  What  would  you  expect  as 
to  the  movement  of  the  winds  with  respect  to  a  region  that  is 
warmer  than  its  surrounding  oceans  ?  colder  than  its  surrounding 
oceans  ?  (DE,  58.8- ;  DP,  42.2-  ;  G,  262.2- ;  T,  257.1-.)  5.  Do 
the  winds  of  S.,  E.,  and  N.  Asia  and  the  neighboring  oceans,  as 
shown  in  32 1  and  2,  confirm  the  answers  to  the  preceding  question  ? 
6.  What  is  the  direction  of  the  winds  in  China  and  on  the  neigh- 
boring sea  in  January  ?  in  July  ?  7.  What  name  may  be  given  to 
these  winds  ?  8.  In  what  months  would  you  expect  most  rainfall 
in  this  region  ?  Why  ?  9.  In  what  months  would  you  expect  the 
most  rainfall  in  S.  Asia?  Why?  10.  On  which  coast  of  India 


128  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

(SE.  or  SW.)  would  you  expect  most  rainfall?  Why?  11.  What 
reasons  can  you  give  for  expecting  an  unusually  heavy  rainfall  on 
the  S.  slope  of  the  Himalayas  in  July  ?  12.  To  what  great  monsoon 
system  do  the  monsoons  of  the  1ST.  Indian  ocean  and  the  NW.  Pacific 
ocean  belong  ?  13.  What  amount  of  rainfall  would  you  expect  in 
central  Asia  in  the  colder  half  year  ?  Explain.  14.  WThat  amount 
would  you  expect  in  the  warmer  half  year  ?  Explain.  15.  What  can 
you  say  about  central  Asia  as  to  its  habitability  ?  16.  How  is  its 
habitability  affected  by  the  size  of  the  continent  ?  by  the  prevail- 
ing winds  ?  by  the  distribution  of  mountains  ?  (See  Plate  45.) 
17.  What  desert  occupies  the  central  part  of  this  continent  ?  What 
mountain  ranges  border  this  desert  ?  18.  What  smaller  continent 
than  Asia  illustrates  the  problems  of  question  4?  19.  Why  do  the 
plains  of  New  Mexico  and  Colorado  receive  only  a  light  rainfall  ? 
20.  Why  does  Arizona  receive  only  a  very  small  rainfall  ? 

10.  Define  :  Preliminary  §,  windward,  leeward  ;  §  2,  wind  belt, 
trade-wind  belt,  belts  of  prevailing  westerly  winds,  doldrums,  horse 
latitudes  ;  §  4,  rainfall;  [§  7,  subequatorial  belt,  subtropical  belts;] 
§  8,  monsoons. 


EXERCISE  XII.    WEATHER  MAPS 

OBJECT.    To  study  the  causes  of  weather  changes. 

Preliminary.  The  four  figures  of  Plate  33  represent  certain 
weather  elements,  such  as  might  be  determined  by  observations 
taken  at  the  same  hour  at  many  different  points  in  the  central 
and  eastern  United  States  on  a  first,  second,  third,  and  fifth  day. 
The  chief  weather  elements  are  the  temperature  of  the  lower  air 
(DE,  28.3,  31.6,  74.8  ;  DP,  27.1-,  48.5-  ;  G,  238.2,  246.3  ;  T,  275.3, 
420.3),  pressure  of  the  atmosphere  (DE,  24.8-;  DP,  23.4-;  G, 
225.6,  253.5-  ;  T,  231.1-,  255.3),  direction  and  strength  of  the  wind 
(DE,  37.9-  ;  DP,  44.4  ;  G,  256.9-),  and  state  of  the  sky  (clear, 
cloudy,  rain,  or  snow).  Atmospheric  pressure,  as  measured  by  the 
barometer,  is  expressed  in  "  inches  of  mercury "  ;  the  values  or 
"readings"  usually  found  are  about  29  or  30  inches.  These  are 
given  in  Plate  33  to  tenths  of  an  inch ;  30.2  is  printed  0.2 ;  29.7, 
as  9.7.  On  government  weather  maps  pressure  is  given  to  hun- 
dredths  of  an  inch.  The  places  or  "  stations  "  of  observation  are 
represented  on  Plate  33  by  the  decimal  points  of  the  barometer 
readings.  The  winds  are  named  by  the  direction  from  which  they 
blow.  Wind  arrows  fly  with  the  wind  ;  the  stronger  the  wind,  the 
longer  the  arrow.  (See  length  of  arrow  for  a  wind  of  20  mi.  an 
hour,  in  SE.  corner  of  33 1.)  Isotherms  (see  Exercise  X,  §  1)  are 
printed  in  fine  dotted  lines  ;  their  values  are  indicated  by  numbers, 
meaning  Fahrenheit  degrees,  as  30,  40,  50,  at  their  ends.  The  scale 
of  these  weather  maps  may  be  taken  as  320  mi.  to  an  inch.  This 
exercise  uses  only  Plate  33. 

1.  NOTE  :  The  pressure  of  the  atmosphere  (the  observations  hav- 
ing been  reduced  to  a  common  standard,  to  make  them  comparable) 
is  indicated  for  various  places  in  33 1.  1.  In  what  part  of  the  map 

129 


130  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

is  the  pressure  more  than  30.0  ?  less  than  30.0  ?  2.  Complete  the 
line  through  points  (0.0)  where  the  pressure  is  30.0.  Such  a  line  is 
called  an  isobaric  line,  or  isobar.  Why  ?  3.  Draw  full  black  lines 
in  33 1  for  the  isobars  of  30.1,  30.2,  30.3.  4.  What  is  the  form  of  the 
isobar  of  30.3  ?  Draw  in  similar  form  but  smaller  size  the  isobar  of 
30.4.  5.  Draw  isobars  for  29.9,  29.8,  29.7.  6.  What  is  the  form  of 
the  isobar  of  29.7  ?  Draw  in  similar  form  but  smaller  size  the  iso- 
bars for  29.6,  29.5,  29.4.  7.  Print  A  in  the  center  of  highest  pres- 
sure ;  C  in  the  center  of  lowest  pressure.  8.  Shade  lightly  [red]  the 
area  within  the  isobar  of  30.3  ;  and  [blue]  the  area  within  the  iso- 
bar of  29.7.  9.  Print  HIGH  and  LOW  in  these  areas.  10.  Describe 
briefly  the  dimensions  and  location  of  the  areas  of  high  and  of  low 
pressure. 

2.  1.  Draw  a  gently  curving  [red]  line  from  the  center  of  high 
pressure  to  the  center  of  low  pressure,  crossing  the  isobars  at  right 
angles.  2.  Why  may  this  line  be  called  a  line  of  pressure  decrease, 
or  of  pressure  gradient,  or  of  barometric,  gradient  ?  3.  What  is  the 
distance  in  miles  between  the  centers  of  high  and  low  pressure  ? 
4.  How  much  decrease  of  pressure  occurs  along  the  line  ?  5.  What 
is  the  average  decrease  of  pressure  in  100  mi.  ?  6.  In  what  part  of 
the  map,  with  respect  to  the  centers  of  high  and  low  pressure,  is 
the  pressure  decrease  gradual  (or  barometric  gradient  weak)  ? 
is  the  pressure  decrease  rapid  (or  barometric  gradient  strong)  ? 
How  can  you  tell  ?  7.  Draw  several  other  lines  of  barometric 
gradient  outward  from  the  center  of  high  pressure ;  inward  toward 
the  center  of  low  pressure.  8.  Are  the  barometric  gradients  rela- 
tively strong  or  weak  in  the  area  of  high  pressure  ?  in  the  area  of 
low  pressure  ?  9.  What  is  the  general  velocity  of  the  wind  in  the 
area  of  low  pressure  ?  10.  What  strength  of  wind  is  indicated 
about  the  center  of  high  pressure  near  the  isobar  of  30.4  ?  near 
the  isobar  of  30.3  ?  11.  What  general  relation  seems  to  obtain 
between  strength  of  barometric  gradient  and  velocity  of  wind  ? 
12.  What  (apparent)  exception  to  this  rule  is  indicated  within  the 
isobar  of  29.4  ? 


WEATHER  MAPS  131 

3.  1.  Draw  several  light  [blue]  curved  lines  prolonging  the  wind 
arrows  in  33  1,  so  as  to  indicate  the  general  flow  of  the  winds,  espe- 
cially about  the  areas  of  high  and  of  low  pressure.    2.  Do  the  winds 
blow  directly  outward  from  the  center  of  high  pressure  ?  directly 
inward  toward  the  center  of  low  pressure  ?    3.  Turn  the  Atlas,  so 
as  to  look  along  one  of  the  barometric  gradient  lines,  in  the  direc- 
tion of  pressure  decrease.    Do  the  winds  near  this  line  blow  par- 
allel to  it,  to  the  right  of  it,  or  to  the  left  of   it?   4.  Test   the 
answer  to  the  previous   question  in  several  other  parts  of  33 1. 
5.  Make  a  general  rule  stating  the  relation  of  direction  of  wind  to 
direction  of  barometric  gradient ;  another  stating  the  relation  of 
strength  of  wind  to  strength  of  barometric  gradient.    NOTE  :  The 
winds  in  the  area  of  high  pressure  may  be  described  as   "blow- 
ing gently  along  outflowing  clockwise  spirals."    (Clockwise  means 
"  turning  in  the  same  direction  as  the  hands  of  a  clock  " ;  counter- 
clockwise means  "turning  in  the  opposite  direction.")    6.  Make  a 
similar  statement  for  the  winds  in  the  area  of  low  pressure. 

4.  NOTE  :   A  set  of  observations  made  a  day  (24   hours)  later 
than  those  in  33 1  is  given  in  332.    1.  Prolong  the  wind  arrows  in 
light  [bine]  curved  lines  in  different  parts  of  332.  -Draw  similar 
lines  in  intermediate  spaces.    2.  What  indication  do  these  curved 
wind  lines  give  of  the  occurrence  of  an  area  of  low  pressure  ?  of 
an  area  of  high  pressure  ?    3.  Complete  in  33  2  the  large  oval  isobar 
of  29.8,  parts  of  which  are  printed  in  broken  lines.    4.  Complete 
the  smaller  oval  isobar  of  29.5.    5.  Draw  intermediate  isobars  for 
29.6,  29.7  ;  draw  the  isobar  of  29.4  (about  as  far  inside  of  29.5  as 
29.6  is  outside  of  it).    6.  Is  there  room  for  an  isobar  of  29.3  ?  If  so, 
draw  it.    7.  Shade  lightly  [blue]  the  area  of  low  pressure,  inside  of 
the  isobar  of  29.7.    Print  C'  in  the  center  of  low  pressure,  and  LOW 
across  the  area  of  low  pressure.    8.  Complete  the  isobars  for  30.1, 
30.4.    Draw  isobars  for  29.9,  30.0,  30.2,  30.3.     9.  In  what  state 
do  you  think  an  area  of  high  pressure  may  have  its  center  (out- 
side of  border  of  33  2)?    10.  Test  in  33  2  the  rules  made  in  §  3,  ques- 
tion 5,  regarding  the  relations  of  wind  and  barometric  gradient. 


132  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

11.  Draw  a  line  inclosing  all  the  stations  where  rainfall  (rain  or 
snow)  is  indicated  in  a3  2.    In  what  states  is  rainfall  indicated  ? 
(The  rainfall  dots  should  be  somewhat  larger  inside  the  isobar  of 
29.6.)    12.  What  is  the  general  position  of  the  rainfall  area  with 
respect  to  the  center  of   low  pressure  ?    13.  What  general  direc- 
tions have  the  winds  in  the  rainfall  area?    14.  Draw  a  line  sepa- 
rating the  region  where  the  sky  is  clear  from  that  in  which  it  is 
cloudy  or  rainy.    What  is  the  general  position  of  the  clear  region 
with  respect  to  the  center  of  low  pressure  ?    15.  In  what  general 
directions  are  the  winds  blowing  in  the  clear  region  ?    16.  In  what 
part  of  33  2  may  the  weather  be  described  as  stormy  ? 

5.  1.  Examine  the  isotherms  (fine  dotted  lines)  in  332.    What 
season  do  you  think  this   weather  map  represents  ?   2.  In  what 
states  may  snow  be  falling  ?    (DE,  70.2  ;  DP,  45.5 ;  G,  231.2 ;   T, 
249.6.)    3.  Draw  in  light  dotted  [blue]  lines  the  isotherms  for  every 
ten  degrees,  spacing  them  proportionately  between  and  outside  of 
the  printed  isotherms.    (The  isotherms  of  80°  should  appear  only 
in  a  small  SE.  corner  of  the  map.)    Print  their  values  in  small 
figures  at  their  ends.    4.  How  much  difference  of  temperature  is 
there  between  places  in  the  NW.  and  the  SE.  parts  of  the  map  ? 

5.  Draw  a  [blue]  dotted  temperature  gradient  line  across  the  map. 

6.  What  is  the' average  decrease  of  temperature  in  100  mi.  ?    7.  In 
what  states  is  the  temperature   gradient  strongest  ?    What  is  the 
temperature  decrease  in  100  mi.  in  that  part  of  the  map  ?   8.  What 
is  the  general  direction  of  the  winds  in  33  2  where  temperatures  are 
above  40°  ?  below  20°  ?   9.  What  relation  seems  to  obtain  between 
wind  direction  and  temperature  ?    10.  Prolong  the  southerly  wind 
arrows  backward,  outside  of  the  map.    From  what  region  do  they 
come?    11.  Answer  the  same   question  for   the  northerly  winds. 

12.  How  can  you  account  for  the   unlike  temperatures   of  these 
winds  ?    (Examine  31 1.)    13.  Now  explain  why  the  strongest  tem- 
perature gradients  occur  in  a  certain  part  of  33  2. 

6.  1.  On  which  side  of  the  center  of  low  pressure  in  33  1  would 
you  expect  relatively  warm,  cloudy,  and  wet  weather  ?  cold,  clear, 


WEATHER  MAPS  133 

and  dry  weather  ?  2.  Mark  C  in  33  2  to  show  the  location  of  the 
center  of  low  pressure  in  33  1.  Draw  a  broken  line  in  33  2  connect- 
ing C  and  C'.  3.  Why  may  this  line  be  called  the  track  of  the 
low-pressure  center,  or  the  storm  track  ?  Prolong  the  track  to  the 
WSW.  and  ENE.  4.  In  what  direction  has  the  center  of  low  pres- 
sure moved  ?  How  far  has  it  moved  in  a  day  (24  hours)  ?  How  far, 
on  the  average,  in  an  hour?  5.  Draw  in  33 1  a  rainfall  area  some- 
what smaller  than  that  of  33  2,  but  in  about  the  same  position  with 
respect  to  the  center  of  low  pressure.  Mark  some  rainfall  dots  in 
this  area  (larger  near  C,  smaller  farther  away).  6.  Mark  some 
clear-weather  signs  E.  of  the  isobar  of  30.0.  7.  Draw  a  light  [blue] 
dotted  isotherm  of  30°  running  NE.-SW.  through  the  center  of  low 
pressure  in  33  1 ;  curve  it  to  E.  across  S.  Lake  Michigan  ;  SE.  across 
Ohio  and  Virginia.  Draw  isotherms  of  70°  and  0°  at  about  the  same 
distances  from  the  isotherm  of  30°  as  they  are  in  33  2.  8.  Describe 
the  weather  of  SW.  Missouri  in  33 1 ;  in  33  2.  9.  How  has  the 
weather  there  changed  in  24  hours,  as  to  temperature  ?  pressure? 
wind  ?  sky  ?  rainfall  ?  10.  How  are  these  changes  related  to  the 
movement  of  the  low-pressure  area?  11.  Describe  the  weather 
of  SW.  Pennsylvania  in  33  1;  in  332.  12.  How  has  the  weather 
there  changed  in  24  hours  as  to  temperature  ?  pressure  ?  wind  ? 
sky  ?  rainfall  ?  13.  How  are  these  changes  related  to  the  move- 
ment of  the  low-pressure  area  ?  14.  Mark  a  cross  on  the  track  of 
the  low-pressure  center,  midway  between  its  positions  on  the  first 
and  second  days.  How  has  the  weather  changed  at  this  cross  in 
24  hours  ?  15.  Is  high  pressure  or  low  pressure  associated  with 
fair  weather  ?  with  stormy  weather  ? 

7.  [1.  Draw  two  lines  parallel  to  the  track  of  the  low-pressure 
center ;  one  about  200  mi.  to  the  N.,  the  other  as  far  to  the  S. 
Mark  crosses  on  these  lines  opposite  the  cross  at  the  midway  point 
of  the  track.  2.  Determine  the  changes  of  wind  direction  at  these 
two  crosses  during  the  24  hours  from  33  1  to  33  2.  3.  Compare  these 
wind  changes  with  those  occurring  at  the  cross  on  the  track.  NOTE  : 
When  the  wind  changes  or  shifts  from  E.  through  SE.,  S.,  SW.,  W., 

'/  i 


134  EXERCISES  IX  PHYSICAL  GEOGRAPHY 

to  NW.,  it  is  said  to  veer;  when  it  shifts  from  E.  through  ISTE.,  N., 
to  NW.,  it  is  said  to  luck.  4.  At  which  cross  in  33  2  does  the  wind 
veer,  as  the  low-pressure  center  passes  eastward  ?  At  which  cross 
does  the  wind  back  ?  5.  Where  in  the  area  of  low  pressure,  33  2,  is 
the  air  calm  ?  G.  Where  is  a  similar  calm  space  indicated  in  33  1  ? 
NOTE  :  It  happens  not  infrequently  that  a  space  of  about  100  mi. 
diameter  at  the  center  of  low  pressure,  or  storm  center,  has  light 
winds  or  calm  air,  and  that  the  rainfall  ceases  there  and  the  clouds 
break;  hence  this  space  has  been  .called  the  eye  of  the  storm.  7.  In 
what  direction  and  with  what  velocity  is  the  wind  blowing  about 
70  mi.  E.  of  the  storm  center  in  33  1  or  33  2  ?  N.  of  the  center  ? 
W.  of  the  center  ?  S.  of  the  center  ?  8.  With  these  facts  in  mind, 
correct,  if  necessary,  your  answer  to  question  14,  §  6,  as  to  the 
change  in  the  winds  as  the  storm  center  passes  by.] 

8.  1.  Draw  additional  wind  arrows  in  the  E.  part  of  33  3,  bearing 
in  mind  the  rules  made  in  answer  to  question  5,  §  3.  2.  Shade 
lightly  [red]  the  area  of  (moderately)  high  pressure  within  the 
isobar  of  30.1,  and  [blue]  the  area  of  low  pressure  within  the  isobar 
of  29.7.  3.  In  what  state  do  you  think  the  center  of  low  pressure 
would  be  found  ?  4.  Mark  C"  to  represent  the  center  (near  edge  of 
the  Atlas  page).  Estimate  the  pressure  at  C".  5.  Print  C  and  C' 
in  33  3  in  the  positions  they  had  in  33  1  and  33  2.  Connect  C,  C',  C",. 
by  a  storm-track  line.  6.  What  is  the  direction  of  the  storm  track 
on  the  second  day  ?  7.  How  far  has  the  storm  center  moved  on  the 
second  day  ?  8.  What  is  its  average  hourly  velocity  for  the  second 
day  ?  for  the  two  days  ?  9.  Compare  the  size  of  the  area  of  low 
pressure  (within  isotherm  of  29.7)  and  the  pressure  at  the  center  on 
the  three  days.  10.  How  has  this  area  of  low  pressure  changed  as 
it  moved  EN"E.  ?  11.  Do  you  think  the  area  of  high  pressure  in  33  3 
represents  a  new  position  of  the  high-pressure  area  on  33  1,  or  of 
the  high-pressure  area  inferred  to  stand  NW.  of  33  2  ?  Why  ?  12. 
What  features,  already  learned  regarding  the  high-pressure  area  in 
33  1,  are  again  illustrated  by  the  high-pressure  area  of  33  3,  as  to  bar- 
ometric gradients  (direction  and  strength)  ?  as  to  winds  (direction, 


WEATHER  MAPS  135 

strength,  and  general  movement)  ?  state  of  sky  ?  13.  All  these 
features  of  a  high-pressure  area,  taken  together,  are  given  the  name 
anticyclone.  Print  ANTICYCLONE  across  the  area  of  high  pressure 
in  333.  14.  Compare  the  position  of  the  isotherm  of  0°  in  33  1,  2,  3. 
How  is  its  change  of  position  related  to  the  direction  of  the  winds  ? 
to  the  movement  of  the  center  of  low  pressure  ?  NOTE  :  A  fall  of 
temperature  of  20°  or  more  in  24  hours  to  a  value  below  freezing 
(32°),  accompanied  by  brisk  or  strong  NW.  winds,  is  called  a  cold 
wave.  15.  In  (about)  what  part  of  332  is  a  cold  wave  occurring? 
In  what  part  of  :u  3  ?  of  33  1  ?  How  can  you  tell  ?  16.  In  what 
direction  does  a  cold  wave  advance  over  the  central  and  eastern 
United  States  ? 

9.  NOTE  :  The  weather  conditions  of  33  4  are  for  the  fifth  day  in 
this  series  of  observations  (the  fourth  day  is  not  here  mapped). 
1.    Draw  a  number  of  wind  arrows  of  appropriate  direction  and 
length  in  334.    2.   In  what  direction  and   how  far  has    the  anti- 
cyclone of  33  3  moved  in  the  interval  between  33  3  and  4  ?   3.  What 
is  its  average  hourly  velocity  ?   4.  Do  you  think  the  area  of  low 
pressure  on  33  4  corresponds  with  the  one  on  the  other  maps  ?    5. 
What  indications  are  found  in  33  3  that  a  new  area  of  low  pres- 
sure is  approaching  ?    From  what  direction  is  it  probably  coming  ? 
6.    What  features  already  learned  regarding  low-pressure  areas  in 
33  1  and  2  are  again  illustrated  in  334,  as  to  barometric  gradients  ? 
as  to  winds  ?  as  to  state  of  sky  ?    7.  All  these  features  of  a  low- 
pressure   area,    taken    together,    are    frequently    given   the   name 
cyclonic  area  or  cyclone.    Print  CYCLONE  in  its  proper  position 
in  334. 

10.  1.  Compare  the  position  of  the  isotherm  of  30°  in  33  3  and  4. 
How  is  its  change  of  position  related  to  the  direction  of  the  winds  ? 
to  the  movement  of  the  center  of  low  pressure  ?    2.  Why  may  the 
change  thus  illustrated  be  called  a  warm  wave  ?    3.  In  what  states 
was  a  warm  wave  taking  place  in  33  1  ?  in  33  2  ?    4.  Where  may  two 
warm  waves  be  supposed  to  be  taking  place  in  connection  with  33  3  ? 
5.  Where  may  a  cold  wave  be  inferred  in  33  4  ?    6.  Draw  a  cyclonic 


136  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

track  ENE.  from  the  cyclonic  center  in  33  4.  7.  Supposing  that  the 
progress  of  this  cyclone  is  at  about  the  same  rate  as  that  of  33  1,  2, 
indicate  in  33  4  the  position  of  the  cyclonic  center  on  the  sixth  day. 
8.  What  sort  of  weather  (temperature,  pressure,  wind,  sky)  is  indi- 
cated for  Chicago  in  33  4  ?  9.  What  sort  of  weather  will  occur 
probably  at  Chicago  on  the  following  day  ?  10.  What  sort  of  weather 
is  indicated  for  Buffalo  on  334?  11.  What  sort  of  weather  will 
probably  occur  at  Buffalo  one  day  later  than  33  4  ?  two  days  later  ? 
[12.  In  what  part  of  33  4  will  the  winds  veer  as  the  cyclonic  area 
moves  eastward  ?  13.  Will  veering  or  backing  winds  be  more  com- 
mon in  the  United  States  in  connection  with  this  cyclonic  storm  ?] 
11.  NOTE  :  Cyclonic  storms  of  the  kind  here  described  occur 
chiefly  in  the  belts  of  westerly  winds,  and  are  relatively  rare  in 
the  trade-wind  belts  ;  they  are  more  violent  at  sea  than  on  land, 
and  in  winter  than  in  summer.  1.  Are  cyclonic  weather  changes 
more  common  in  Africa  or  in  N.  America  ?  in  S.  America  or  in 
Asia?  Why?  2.  In  what  month  would  cyclones  and  anticy- 
clones control  the  weather  of  the  N.  coast  of  Africa  ?  that  of  the  S. 
coast  ?  3.  What  sort  of  weather  would  probably  be  encountered  by 
a  vessel  rounding  Cape  Horn  (see  Plate  42)  in  January  ?  in  July  ? 

4.  In  what  season  would  the  change  of  temperature  due  to  the  pas- 
sage of  a  cyclonic  storm  in  the  E.  United  States   be  greatest? 
Why  ?   5.  Would  the  change  of  temperature  due  to  the  passage  of 
a  cyclonic  storm  in  January  be  greater  in  the  E.  United  States  or  in 

5.  Europe  ?    Why  ?    6.  Why  can  weather  predictions  be  made  more 
accurately  for  the  E.  United  States  than  for  W.  Europe  ?   7.  In  32 1 
represent  by  [blue]  wind  arrows  a  cyclonic  storm  of  appropriate 
size  (see  33  2)  in  the  N".  Atlantic.    (Place  the  center  of  low  pres- 
sure near  50°  N.  lat.,  40°  W.  long.)  8.  In  32  2  draw  a  similar  cyclonic 
storm  in  the  S.  Atlantic  (on  the  same  meridian  but  in  50°  S.  lat.). 
NOTE  :    Cyclonic  winds  turn  clockwise  in  the   S.  hemisphere.    9. 
Draw  in  32  2  an  anticyclone  of  appropriate  area  (see  33  3)  in  the 
N".  Pacific  (center  of  high  pressure  in  45°  N.  lat.,  180°  long.).   10. 
Draw  a  similar  anticyclone  in  32  1  in  the  S.  Pacific  (on  the  same 


WEATHER  MAPS  137 

meridian  but  in  45°  S.  lat.).  NOTE  :  The  winds  of  anticyclones  in 
the  S.  hemisphere  blow  outward,  in  counter-clockwise  spirals.  11. 
What  would  be  the  direction  of  a  warm  inflowing  wind  in  a  cyclone 
in  the  S.  hemisphere  ?  of  a  cold  inflowing  wind  ?  [12.  What  Avould 
be  the  succession  of  wind  directions  noted  by  an  observer  on  the 
track  of  a  cyclone  in  the  S.  hemisphere  ?  on  the  equatorial  side 
of  the  track  ?  on  the  S.  polar  side  of  the  track  ?  13.  When  one 
observer  has  cloudy  and  wet  weather  in  a  cyclonic  area,  what  sort 
of  weather  will  be  noted  by  another  observer  who  is  under  a  neigh- 
boring anticyclone  ?  14.  As  the  phases  of  the  moon  are  the  same 
for  both  these  observers,  what  does  your  answer  to  the  preceding 
question  suggest  as  to  the  control  of  weather  by  the  moon  ?] 

12.  Define  :  §  1,  isobaric  line,  isobar  ;  §  2,  line  of  pressure  de- 
crease, pressure  gradient,  barometric  gradient  ;  §  3,  clockwise, 
counter-clockwise  ;  §  6,  storm  track  ;  §  7,  veer,  back,  storm  center, 
eye  of  the  storm ;  §  8,  anticyclone,  cold  wave  ;  §  9,  cyclonic  area, 
cyclone  ;  §  10,  warm  wave. 


EXERCISE  XIII.    OCEAN  CURRENTS 

OBJECT.  To  learn  the  general  system  of  ocean  currents,  the  causes 
to  which  they  are  due,  and  their  effects  in  modifying  the  distribution  of 
atmospheric  temperatures. 

Preliminary.  The  surface  waters  in  the  greater  part  of  the  oceans, 
to  a  depth  of  several  hundred  feet,  are  in  slow  movement  at  a  rate 
of  from  10  to  20  or  30,  occasionally  60  or  80,  (nautical)  miles  a  day. 
The  moving  waters  are  called  currents;  but  where  a  current  is 
narrow,  deep,  and  rapid  it  is  called  a  stream;  where  it  is  broad, 
shallow,  and  slow  it  is  called  a  drift.  The  prevailing  direction  of 
ocean  currents  has  been  determined  in  many  parts  of  the  world  by 
the  movement  of  floating  objects,  such  as  the  wrecks  of  vessels,  and 
in  various  other  ways.  The  direction  of  currents  is  stated  in  terms 
of  the  point  of  the  compass  toward  which  they  flow,  as  northward, 
southeastward,  etc.  The  currents  as  charted  in  Plate  34  are  rep- 
resented in  simplified  form,  without  the  irregularities  that  might 
be  shown  on  a  chart  of  larger  scale.  For  the  purposes  of  this  exer- 
cise the  "  polar  oceans  "  will  be  taken  to  extend  to  latitude  55°  N. 
and  S.,  and  the  other  oceans  will  be  sometimes  spoken  of  as  "  non- 
polar  oceans."  Distances  in  the  nonpolar  oceans  on  the  charts  here 
referred  to  may  be  roughly  measured  by  noting  that  40  latitude 
degrees  equal  2400  nautical  miles.  This  exercise  uses  Plate  34. 

1.  1.  What  is  the  general  direction  of  the  ocean  currents  in 
latitude  40°  or  50°  N.  or  S.  ?  of  the  currents  near  the  equator  or 
the  equatorial  currents?  (Do  not  consider  for  the  present  the 
currents  shown  by  waving  lines  near  the  equator.)  2.  What  is  the 
general  direction  of  the  currents  near  the  eastern  side  of  the  non- 
polar  oceans  ?  near  the  western  side  ?  (Use  equatorward  and  pole- 
ward, instead  of  northward  and  southward,  in  answering  this 

138 


OCEAN   CURRENTS  139 

question.)  3.  Describe  the  general  motion  of  the  currents,  when 
taken  together,  in  each  N.  nonpolar  ocean  ;  in  each  S.  nonpolar 
ocean.  (Omit  the  N.  part  of  the  Indian  ocean  for  the  present.)  4. 
If  you  visited  the  central  part  of  a  nonpolar  ocean  and  could  see 
the  currents  moving  around  you,  in  which  oceans  would  they  turn 
clockwise  (with  the  hands  of  a  clock)?  in  which  counter-clockwise? 
[5.  If  you  stood  at  the  N.  pole  and  could  see  the  earth  turning  in 
its  daily  rotation,  would  it  appear  to  turn  clockwise  or  the  other 
way  ?  6.  How  would  it  appear  to  turn  if  you  stood  at  the  S.  pole  ? 
7.  Compare  the  turning  of  the  earth,  as  seen  from  the  N.  pole,  with 
the  turning  of  the  currents  in  the  two  N.  nonpolar  oceans.  8. 
Make  the  same  comparison  for  the  S.  hemisphere.]  9.  Draw  in 
the  X.  and  S.  nonpolar  oceans  of  the  ideal  diagram,  342,  some 
circular  lines,  with  arrowheads,  to  show  the  general  movement  of 
currents  appropriate  to  each  ocean  there  mapped.  In  the  center  of 
each  ocean  draw  a  small  circle,  imitating  a  clock  face,  and  indicate 
upon  it  direction  of  clockwise  motion.  NOTE  :  The  general  turning 
movement  of  the  currents  in  each  ocean  may  be  called  eddies.  [10. 
About  how  long  would  it  take  a  floating  object  to  make  a  circuit  of 
the  1ST.  Atlantic  eddy  ?  See  the  velocities  stated  in  the  preliminary 
section  ;  estimate  length  of  circuit  in  terms  of  degrees  of  latitude, 
and  change  degrees  to  nautical  miles  (60  to  a  degree).]  11.  Should 
the  eddies  be  described  as  fast  moving  or  as  slow  moving  ? 

2.  1.  Examine  the  currents  in  50°  or  60°  S.  lat.  in  34 1.  (They 
will  be  better  understood  if  examined  on  a  globe.)  If  these  currents 
were  seen  by  an  observer  stationed  at  the  S.  Pole,  how  might  he 
describe  their  general  movement  ?  [2.  How  does  their  movement 
compare  with  the  direction  of  the  earth's  rotation  ?]  3.  Why 
may  these  currents  taken  together  be  called  the  Antarctic  eddy  ? 
4.  Do  they  seem  to  form  a  stream  or  a  drift  ?  5.  How  is  the  Ant- 
arctic eddy  related  to  the  three  eddies  of  the  S.  nonpolar  oceans  ? 
6.  Why  is  there  not  an  Arctic  eddy,  corresponding  in  size  to 
the  Antarctic  eddy  ?  NOTE  :  There  is  believed  to  be  a  relatively 
small  Arctic  eddy,  flowing  in  a  general  way  eastward  around  the 


140  EXERCISES   IN  PHYSICAL  GEOGRAPHY 

Arctic  ocean.  7.  Draw  a  light  pencil  line  around  the  general 
course  of  the  eddy  in  the  N.  Pacific  ocean  in  34  1.  8.  Is  the  course 
circular  or  oval  ?  9.  About  how  wide  is  it  N.-S.?  how  wide  E.-W.  ? 

10.  The  W.  part  of  this  eddy  is  called  the  Japanese  current.  Why  ? 

11.  Describe  the  local  currents  in  the  NE.  and  NW.  parts  of  the 
N.  Pacific,  in  their  relation  to  the  main  eddy.    12.  Draw  a  line 
around  the  best  defined  eddy  of  the  S.  Pacific.    What  part  of  the 
ocean  does  this  eddy  occupy  ?    13.  What  are  its  rough  dimensions 
N.-S.  ?   E.-W.  ?    14.  The  eastern  part  of  this  eddy  is  called  the 
Peruvian  current.    Why  ?    15.  What  reasons  can  you  suggest  for 
the  occurrence  of  a  smaller  eddy  in  the  W.  part  of  this  ocean  ? 

3.  1.  Draw  a  pencil  line  around  the  eddy  of  the  Indian  ocean  in 
34  1.  What  are  its  rough  dimensions  ?  2.  How  is  it  connected  with 
the  eddy  of  the  Pacific  ocean  ?  3.  How  are  its  currents  related  to 
Madagascar  ?  to  the  S.  point  of  Africa  ?  4.  Draw  a  pencil  line 
around  the  S.  Atlantic  eddy.  What  are  its  rough  dimensions  ? 

5.  How  does  its  shape  differ  from  that  of  the  Indian  ocean  eddy  ? 

6.  Does  it  receive  a  branch  from  the  Indian  ocean  ?    7.    How  does 
its  SW.  part  differ  from  the  corresponding  part  of  the  S.  Pacific 
eddy  ?   8.  Draw  a  pencil  line  around  the  N.  Atlantic  eddy.    What 
are  its  rough  dimensions  ?    9.  What  islands,  sea,  and  gulf  are  on 
the  SW.  side  of  the  N.  Atlantic  ?    10.  How  are  the  currents  of 
the  N.  Atlantic  eddy  related  to  these  islands  and  seas  ?    11.  The 
W.  part  of  the  N.  Atlantic  eddy,  along  the  E.  coast  of  the  United 
States,  is  called  the  Gulf  stream.    Why  ?    12.  Compare  the  breadth 
of  the    Gulf   stream  with   that   of   the  currents    W.   of   Europe. 
13.  Why  may  the  last-named  currents  be  appropriately  called  the 
N.  Atlantic  drift?    14.  How  are  the  two  Atlantic  eddies  connected  ? 
15.  What  influence  have  the  outlines  of  the  bordering  continents 
in  causing  the  connecting  current  to  cross  the  equator  ?    [16.  Draw 
in  34  2  a  new  [red]  outline  of  the  continents  there  shown,  so  that 
the  eddy  of  the  N".  ocean  shall  give  out  a  cross-equator  connecting 
current  to  the  eddy  of  the  S.  ocean ;  indicate  this  branch  by  [blue] 
arrows.     In  what  direction  does  this  connecting  current  flow  ?    In 


OCEAN  CURRENTS  141 

what  direction  does  the  actual  connecting  current  flow  across  the 
equator  in  the  Atlantic  ocean  ?] 

4.  1.  Compare  the  currents  N.  of  the  N.  Atlantic  eddy  with  those 
N.  of  the  N.  Pacific  eddy,  as  to  position  ;  as  to  direction  ;  as  to 
dimensions.    2.  Which  of  these  far-northern  currents  may  be  de- 
scribed  as   an  outgoing,    poleward    branch   of    the    main    eddy  ? 

3.  Which   may   be   described   as   wedging   equatorward    currents 
between  the  main  eddy  and  the  neighboring  continent?    4.  Which 
eddy  of  the  S.  oceans  has  an  outgoing  poleward  branch  ?   Why  does 
it  occur  in  this  ocean  and  not  in  the  others  ?    5.  Compare  its  di- 
mensions and  position  with  those  of  the  outgoing  branch  of  the 
N.  oceans.     6.  Which  ocean  has  the   largest  outgoing  poleward 
branch  from  its  main  eddy  ?    Why  ?     7.  How  does  this  branch 
seem  to  be  connected  with  the    eddy  of   the- neighboring   polar 
ocean  ?    8.  Which  of  the  S.  oceans  receives  an  equatorward  wedg- 
ing current '.'    9.  How  is  the  wedging  current  related  to  S.  America? 

10.  Why  is   such  a  current  not  found  in  the  other   S.  oceans  ? 

11.  Compare  the  breadth  of  open  water  connecting  the  N.  Atlantic 
and  the  Arctic  with  that  connecting  the  N.  Pacific  and  the  Arctic. 

12.  What  currents  are  indicated  in  34  1  in  Bering  strait  ?    (Such 
currents  as  occur  there  are  small  and  unimportant  in  the  general 
system  of  ocean  currents.)    13.  Compare  the  eddies  of  the  two  polar 
oceans  as  to  size  ;  as  to  breadth  of  connection  with  the  eddies 
of   neighboring   oceans.     14.  What    influence    has  the  S.  end  of 
S.  America  on   the    eddies   of   the   neighboring   oceans  ?    Why  ? 
15.  What  influence   has  the  E.   point  of  S.  America  (Cape  San 
Roque)  on  the  eddies  of  the  Atlantic? 

5.  1.  Compare  the  general  direction  of  the  prevailing  winds  in 
far  S.  latitudes,  as  shown  in  32  1  and  2,  with  the  general  circulation 
of  the  ocean  currents  in  the  S.  polar  (Antarctic)  eddy.     2.  Do  the 
same  for  the  three  S.  oceans  ;  for  the  two  N.  oceans.     3.  Mark 
[blue]  dots  in  34 1  where  the  winds  and  currents  have  a  general 
agreement  in  direction  ;  mark  small  [red]  crosses  where  they  differ. 

4.  Do  the  winds  and  currents  generally  agree  or  differ  in  direction  ? 


142  EXERCISES  IN  PHYSICAL  GEOGRAPHY 

5.  Which  ordinarily  has  the  greater  velocity,  the  prevailing  winds 
or  the  ocean  currents  ?  6.  What  do  the  answers  to  questions  4  and 
5  suggest  as  to  the  cause  of  the  ocean  currents  ?  7.  Examine  the 
small  current  of  the  Indian  ocean,  near  the  equator,  for  January, 
as  shown  by  waving  lines  in  34  5.  Why  may  this  current  be  called 
an  equatorial  counter  current  ?  8.  What  is  its  position  with  respect 
to  the  equator  ?  9.  What  is  the  direction  of  the  winds  in  the  same 
part  of  the  ocean  and  in  the  same  month  ?  (See  34  3.)  10.  What  are 
the  names  of  the  two  large  N.  embayments  of  the  Indian  ocean  ? 
(See  Plate  44.)  11.  In  what  month  is  the  counter  current  of  the 
Indian  ocean  K.  of  the  equator  ?  Describe  its  course.  12.  How 
do  the  winds  blow  in  that  part  of  the  ocean  at  that  time  ?  13.  How 
do  the  facts  just  learned  bear  on  the  answer  given  to  question  6  ? 

6.  [1.  In  what  other  oceans  do  equatorial  counter  currents  occur  ? 
(See  34  7  and  8.)     2.  Describe  the  counter  current  of  the  Atlantic 
in  January  ;  in  July.    3.  In  which  of  these  months  are  the  SE.  trade 
winds  extended  over  the  greatest  area  K.  of  the  equator  ?    (See 
32 1  and  2.)     4.  What  connection  appears  to  exist  between  these 
extended  trade  winds  and  the  counter  current  of  the  Atlantic  ? 

5.  Describe  the  counter  currents  of  the  Pacific  in  January  ;  in  July. 

6.  Where  does  the  counter  current  in  the  Pacific,  S.  of  the  equator 
in  January,  stand  in  relation  to  the  extension  of  the  NE.  trade 
winds  S.  of  the  equator  ?    7.  What  are  the  directions  of  the  winds 
and  currents  in  this  part  of  the  ocean  in  July?    8.  Compare  the 
counter  current  of  the  Pacific  N.  of  the  equator  in  January  and  July. 
In  which  month  has  this  counter  current  its  greatest  development  ? 
9.  What  general  relation  appears  to  exist  between  the  extension  of 
the  trade  winds  across  the  equator,  in  the  form  of  more  or  less 
perfectly  developed  monsoon  winds,  and  the  occurrence  of  equa- 
torial counter  currents  ?     10.  In  what  parts  of  what  oceans  is  this 
relation  found  ?    in  what  months  ?] 

7.  1.  On  which  side  of  the  various  current  eddies,  E.  or  W.,  would 
you  expect  to  find  relatively  cool  water  ?  relatively  warm  water  ? 
Why  ?    2.  Mark  broken  [or  blue]   arrows  on  the  cool  currents  ; 


OCEAN  CURRENTS  143 

full-line  [or  red]  arrows  on  the  warm  currents.  3.  On  which  side, 
E.  or  W.,  of  the  torrid  oceans  should  the  equatorial  currents  have 
the  highest  temperature  ?  4.  Mark  [red]  arrows  along  the  equato- 
rial currents  in  that  half  of  their  course.  NOTE  :  The  mean  annual 
temperature  of  the  ocean  surface  is  shown  by  dotted  isotherms 
in  34 1.  5.  Shade  [red]  the  area  over  80°  and  [blue]  under  40°. 
6.  Why  do  the  isotherms  of  70°  turn  towards  the  equator  in  the 
N.  and  in  the  S.  Atlantic  ?  in  the  N.  and  the  S.  Pacific  ?  7.  Why 
is  the  80°  isotherm  in  the  torrid  Pacific  limited  to  its  W.  part? 
8.  Why  is  the  40°  isotherm  deflected  to  an  oblique  course  in  the 
N.  Pacific  ?  9.  Why  is  the  deflection  of  the  40°  isotherm  stronger 
in  the  N.  Atlantic  than  in  the  N.  Pacific  ? 

8.  1.  Examine  the  mean  annual  temperatures  of  the  lower  atmos- 
phere in  30  2.    Why  are  the  isotherms  of  80°  nearer  together  on  the 
E.  side  than  on  the  W.  side  of  the  torrid  Atlantic  ? '  2.  On  which 
side  (E.  or  W.)  of  the  nonpolar  oceans  are  the  isotherms  of  70° 
deflected  equatorward  ?  Why  ?   3.  Where  is  the  deflection  greatest  ? 
Why  ?    4.  Why  is  the  40°  isotherm  deflected  to  an  oblique  course 
over  the  N.  Pacific  ?    5.  Why  is  the  deflection  of  this  isotherm 
greatest  in  the  N.  Atlantic  ?   6.  Over  what  ocean  is  the  30°  isotherm 
deflected  to  the  greatest  distance  from  the  equator  ?  Why  ?    7.  Why 
is  there  no  corresponding  deflection  of  the  30°  isotherm  over  the 
S.  Atlantic  ?    8.  Why  are  the  isotherms  of  40°  and  70°  closer  to- 
gether on  the  W.  side  of  the  N.  Pacific  and  N.  Atlantic  than  on 
the  E.  side  of  these  oceans  ?    9.  Why  are  the  corresponding  iso- 
therms over  the  Indian  ocean  so  nearly  parallel,  instead  of  divergent, 
as  over  the  1ST.  oceans  ?   NOTE:  The  annual  change  of  temperature 
in  the  ocean  surface  is  much  less  than  in  the  atmosphere.    10.  On 
which  side  (E.  or  W.)  of  the  N.  continents  is  the  annual  range  of 
atmospheric  temperature  smallest?    (See  30  3.)  Why  ? 

9.  1.  Examine  31 1.    Why   does    the   January   isotherm   of  20° 
occur  N.  of  Norway  in  the  same  latitude  as  that  of  —  30°,  N.  of 
Alaska?    2.  Why  is  the  January  temperature  gradient  in  Alaska 
so  much  stronger  than  in  Norway  ?    3.  Suppose  a  sailing  vessel 


144  EXERCISES  IX  PHYSICAL  GEOGRAPHY 

from  a  X.  Atlantic  port  is  bound  for  an  Australian  port  ;  describe 
its  course,  so  that  it  may  take  best  advantage  of  winds  and  currents 
S.  of  lat.  30°  S.  Explain.  4.  In  what  months  might  small  sailing 
vessels  most  easily  make  the  voyage  from  India  to  equatorial 
Africa  ?  the  return  voyage  ?  Why  ?  5.  If  a  sailing  vessel  made  a 
voyage  from  San  Francisco  to  Japan  and  back,  on  which  trip  should 
it  follow  a  more  northern  course  ?  Why  ?  [6.  If  a  sailing  vessel, 
bound  from  New  York  to  Buenos  Aires  (see  Plate  42),  attempted  to 
cross  the  equator  N".  of  Cape  San  Koque,  what  sort  of  winds  might 
it  find  on  the  heat  equator  ?  7.  How  might  the  vessel  be  drifted 
by  the  currents  in  that  part  of  the  ocean  ?  8.  Would  it  thus  be 
helped  or  hindered  on  its  voyage  ?  9.  Where  should  the  equator  be 
crossed  by  such  a  vessel  ?] 

10.  Define  :  Preliminary  §,  currents,  stream,  drift  ;  §  1,  equato- 
rial current,  clockwise,  counter-clockwise,  eddy  ;  §  3,  Gulf  stream, 
N.  Atlantic  drift ;  §  5,  equatorial  counter  current. 


INDEX 


Africa,  33,  85,  116,  123- 

125,  127,  144 
aggradation,  10,  52 
Alabama,  42 
Alaska,  143 
Algeria,  126 

Allegheny  mountains,  93 
Allegheny  plateau,  42,  43 
alluvial  deposits,  36,  50, 

52 
alluvial  fans,  36,  52,  54, 

59,  61 

Alps,  56,  57 
America.    See  North 

America   and   South 

America 
amphitheater,  61 
Andes,  124 

Antarctic  ocean,  139,  141 
Antarctic  regions,  116 
anticyclone,  135-137 
Arctic  ocean,  139,  140 
Arctic  regions,  116 
Ardennes,  51 
areas   of    high    and   low 

pressure,  130-137 
Arizona,  35,  68,  128 
Arkansas  river,  54 
artesian  wells,  22 
Asia,    55,   60,    116,    117, 

122,  127 
Atlantic  ocean,  117,  121, 

123,139,140,141,143 
Australia,  116,  124,  126, 

127,  144 

Bar,  111 
barometer,  129 
barometric  gradient,  130, 

131 
barrier  beach,  100,  104 


baselevel,  5,  19,  41,  45, 

63,  107 
local,  6,  82 

basin,  50,  59 
interior,  10 

beach,  100,  106-108,  134 

belt,  subequatorial,  125 
subtropical,  125,  126 
trade-wind,  122,  123 
westerly  wind,  122,  123 

Berea,  22 

Bering  strait,  141 

Black  mountains,  61 

Blue  ridge,  85,  94 

Bogota,  126 

Boothbay,  98 

Borneo,  124 

bowlders,  6,  36 

Brazil,  126 

Buenos  Aires,  144 

butte,  41 

Caldera,  74,  75 
California,  48,  50,  51,  54, 

59,  68,   70,   76,   106, 

124,  126 
calms,  122,  124 
Canada,  78 
Cantal,  73 

canyons,  29-44,  49,  107 
Cape  San  Roque,  141,  144 
Cape  Town,  126 
capture,  river,  88-92 
cascade,  21 

Cascade  mountains,  56 
cave,  34,  35,  99 
Central  America,  70,  123, 

124 

Ce"vennes,  56 
chasm,  99 
Cheat  river,  44 
145 


Chile,  126 
China,  53,  127 
cliff,  29,  34,  76,  107 
cliff  dwelling,  35 
cliff  maker,  32 
cliffs,  recession  of,  31 

retreat  of,  31 

sea,  98-113. 

elevated  sea,  119 
clockwise,  131,  136,  139 
coast,  9,  96-114,  124 

embayed,  97 

coastal  plain,  13-17,  18- 
28,  109-112 

lacustrine,  22,  113 
cold  wave,  135 
Colorado,  35,  41-43,  49, 
54,  59,  74,  76,  77,  128 
Colorado  river,  35 
contour,  13,  40,  97 
contour  line,  13 
contour  interval,  13 
counter-clockwise,    131, 

137,  139 

counter  currents,  142 
country  rock,  76 
cove,  99 
crater,  66,  74 
Crater  lake,  76 
crest  line,  56 
Cuba,  109 
currents,  111,  138-144 

equatorial,  138 

tidal,  101,  111 
cycle  of  erosion,  8,  9,  46, 
64,  65,  79,  87,  95,  97, 
113 

cyclone,  135-137 
cyclonic  areo,,  135 

Deception  island,  76 


146 


EXERCISES  IN   PHYSICAL  GEOGRAPHY 


degradation,  5,  52 

flood   plain,    18,   45,   62, 

January     temperatures, 

delta,    6,    102,    103,    106, 

63 

117-120 

111,  112 

formation,  30,  32,  82 

January  winds,  121-128 

deposition,  6 

fossils,  14,  30 

Japan,  70,  144 

depression  of  land,  109,  1  13 

France,  51,  55-57,  73 

Japanese  current,  140 

desert,  124,  128 

Fujiyama,  70 

Jhelam  river,  60 

dike,  71,  78 

Jorullo,  68,  75 

dissection,  26,  39,  70,  75 

Georgia,  65 

July   temperatures,   117- 

diversion,  90 

Germany,  63 

120 

divide,  -4,  26,  40,  51,  55, 

Golden  Gate,  106 

July  winds,  121-128 

63,  64,  89,  92 

gorge,  49,  53,  54,  58,  69, 

junction  of  rivers,  4 

creeping,  91 

70,  82,  107 

accordant,  4,  53,  58 

definite,  55,  89 

grade,  20,  60,  62,  84 

hanging,  4,  53,  58 

indefinite,  55,  89 

gradient,  pressure,  130 

leaping,  91 

temperature,  116 

Kanawha  river,  44 

longitudinal,  94 

gravel,  6,  76 

Kashmir,  60 

doldrums,  123,  125 

gravel  reef,  100 

Kentucky,  42 

drainage  area,  92 

Greenland,  120 

drift,  138,  140 

Gulf  of  Mexico,  121 

Labrador,  120 

Gulf  stream,  140 

lacustrine    coastal   plain, 

Eddies,  139-142 

gulley,  24 

22,  113 

Elands  river,  85 

lagoon,  101,103-105,  110- 

elbow  of  capture,  91,  92 

Hachures,  10,  40,  97 

113 

elevation    of    land,    109, 

hanging  valley,  4,  53,  58 

lake,  10,  50,  56,  58,  67- 

112,  113 

harbor,  105,  106,  113 

70,  81,  83,  86,  104 

Enchanted  Mesa,  44 

Harpers  Ferry,  85 

landslide,  56,  58,  102 

equatorial  current,  138 

Hawaii,  124 

lava  cascade,  68 

equatorial    counter    cur- 

headland, 96,  97,  104,  105 

lava  flows,  66-79 

rent,  142 

heat     equator,     117-119, 

leeward,  121 

equatorward,  138 

125-127 

load  of  rivers,  9,  31,  61 

Erie,  lake,  16,  22,  113 

high-pressure   area,    130, 

lobe  of  flood  plain,  62 

erosion,  5 

131,  134 

lowland,  95,  96 

headward,  25,  77,  89 

hill,  6,  8,  96,  108 

low-pressure  area,  130-1  37 

lateral,  62 

Himalayas,  60,  128 

marine,  9,  98-113 

horse  latitudes,  123 

Madagascar,  140 

retrogressive,  25,  77,  89 

hurricane  delta,  111 

Maine,  98 

revived,  54,  82 

Hwang-Ho,  52 

malpais,  71 

river,  5,  20,  80-87,  88- 

map,  10 

95 

Idaho,  73 

marsh,  101 

Europe,  116,  123 

India,  60,  127,  144 

Maryland,  28 

eye  of  a  storm,  134 

Indian   ocean,    126,   128, 

meander,  43,  61,  62 

140,  142,  143 

meander  belt,  62 

Fall  line,  21,  112,  113 

inlet,  101,  111 

mesa,  41,  76 

fall  of  a  plain,  14 

interfluve,  45,  46 

Mesa  de  Maya,  76 

of  a  river,  5,  32,45,  81, 

island,  96 

Meuse  river,  51 

111 

land-tied,  103-105 

Mexico,  68,  71,  123,  124 

fall  maker,  32,  82,  84,  85 

isobar,  130,  132,  133 

migrati  on  of  divides,  90,  9  1 

falls,  31,  33,  34,  80-87,  91 

isotherm,   115,   129,   132, 

of  heat  equator,  117-119 

recession  of,  31  ,  76,  85 

133,  143 

Mississippi  river,  23 

retreat  of,  31,  85 

isthmus,  96,  97,  113 

monadnock,  64 

fan,  36,  52,  54,  59,  61 

Italy,  67,  75 

monsoons,  126,  127 

INDEX 


147 


Montana,  56 
Monte  Nuovo,  67 
Morocco,  126 
Mosel  river,  63 
mountains,    1-12,   45-65, 
96,  124 

flat-topped,  55,  57 

subdued,  61 
Mt.  Shasta,  68,  70 
Mt.  Taylor,  76 
mud  flats,  105,  106 

Neck,  67,  75-78 

Nevada,  124 

New  Jersey,  113 

New  Mexico,  35,  44,  76, 

128 

Nicaragua,  lake,  70 
Nile,  125 
North  America,  116,  117, 

123 

North  Carolina,  27,  28,  61 
Norway,  120,  143 

Ocean.    See  Atlantic,  etc. 

ocean    currents,    111, 

138-144 
oceans,  138 

nonpolar,  138 

polar,  138 
offset  reef,  111 
Ohio,  16,  22 
Ohio  river,  43,  113 
oldland,  15,  21,  22,  24 
Oregon,  16,  73,  75,  124 
outcrop,  21,  29,  32 
outlet,  67,  69,  81,  89 
outlier,  39 

Pacific  ocean,  73,  117, 
122, 123, 128, 140, 143 

pass,  56 

Patagonia,  124 

peak,  4,  60,  75 

peneplain,  8,  41,  63,  64,  65 

peninsula,  96,  97, 103, 105 

Pennsylvania,  63,  84;  93, 
94 

Pern,  124 

piedmont  deposits,  59 

pipe,  67,  72 


plain,  basin,  50 

coastal,    13-17,    18-28, 
109-112 

dissected,  26 

lacustrine,  16,  22 
plateaus,  29-44 
platform,  35 
poleward,  138 
Potomac  river,  85,  94 
pressure  gradient,  130 

of  atmosphere,  129 
prevailing  winds,  121-128 
profile,  5,  14,  32,  34,  47, 

49,  58,  83,  94,  99 
Purgatoire  river,  42 

Railroad,  76 

rainfall,    123,    124,    126, 

132 
range  of  mountains,  2 

of  temperature,  120 

of  tides,  99 
rapids,  21,  31,  80,  87 
Raton  mesa,  76 
ravine,  24,  70 
reach,  82,  84,  86 
recession  of  cliffs,  31,  76, 
85,  112 

of  falls,  31,  76,  85 
reef,  96,  97,  100-103,  1HT, 

111,  113 
relief,  9,  45 

retreat  of  cliffs,  31,  76,  85, 
112 

of  falls,  31,  76,  85 
ridge,  4,   55,   57,  69,  60, 

88-95 
rill,  6 
river,  antecedent,  50,  81 

beheaded,  61,  95,  106 

betrunked,  106 

braided,  53 

captured,  88-92 

consequent,  19,  109 

dismembered,  97 

engrafted,  109 

extended,  109 

graded,  20 

insequent,  25 

longitudinal,  92 

mature,  8,  26,  37,  87 


river,  meanders,  43 

misfit,  92 

old,  8,  87 

rejuvenated,  8,  48 

revived,  8,  48,  113 

subsequent,  92 

tidal,  104 

transverse,  92 

young,  8,  37,  87 
river  basin,  4 
river  flood  plain,  18,  45, 

62,63 

river  junctions,  4,  53,  58 
river  mouth,  5,  106,  107 
river  system,  4 
rivulet,  24 

rock  bench,  98-102,  108 
rock  waste,  6,  58,  100 
Rocky  mountains,  49,  54, 

56,  59,  76 
Rocky  river,  22 

Sacramento  river,  51 
San  Antonio  mountains, 

69 

sand,  6,  110 
sand  reef,  100,  106 
sapping,  76,  77 
scale  of  maps,  11,  97 
Scotland,  16,  78 
scroll,  62 
sculpture   of   mountains, 

57 

sea  cliff,  9,  98-113 
section,  34 
Shasta,  Mt.,  68,  70 
Shenandoah  river,  94 
shifting  divides,  90 
shoal,  110 

shore  cliffs.   See  Sea  cliffs 
shore  line,  9,  21,  96-114 

embayed,  27,  97,  112 

initial,  99 

mature,  102,  107 

of  depression,  113 

of  elevation,  112 

young,  99 
Siberia,  64 
Sierra  Nevada,  48,  51,  54, 

76 
silt.  6 


148 


EXERCISES  IX  PHYSICAL   GEOGRAPHY 


skerries,  99 

slopes,  61 

Snake  river,  74 

snow,  132 

Society  islands,  73 

soil,  6,  63 

South  America,  116,  125, 

127,  141 

South  Shetland  islands, 75 
Spanish  peaks,  77 
spit,  101-104,  106 
spur,  4,  60,  61 
stack,  99 
storm,  100,  107,  108,  110, 

132,  134,  136 
storm  center,  134 
storm  track,  133,  134 
strait,  96,  97 
stratum,  7,  21,  29 
stream  junctions,  4,  53,  58 
streams,  4,  25,  30,  44,  46, 

48,  138 

structure,  21,  33,  40,  80 
subdivide,  4,  46,  51,  92 
subequatorial  belt,  125    , 
submergence,  97,  98 
subtropical  belt,  125 
Sumatra,  124 
summer,  118,  123 
surf,  107 

Susquehanna  river,  63,  94 
swell,  107 
Switzerland,  57 

Table  mountain,  73,  76- 

78 

Tahiti,  73 
talus,  31,  107,  109 
Taylor,  Mt.,  76 


temperature,  115, 129, 1 32, 

136,  143 

mean  annual,  116,  143 
temperature  belts,  1 1 6 
temperature  gradient,  1 1 6, 

132 
temperature    range,   120, 

143 

Texas,  111 
texture  of  dissection,  60 

of  waste,  9 
thermometer,  115 
Tian  Shan  mountains,  55 
tidal  current,  111 
tidal  delta,  111 
tidal  inlet,  101,  111 
tidal  range,  99 
tidal  river,  104 
tide.  98,  99,  101,  103,  104 
tide  marsh,  101,  103,  105, 

106,  110,  111 
torrent,  48 
torrid  belt,  116 
trade  winds,  122-127,  136 
transportation,  6 
Transvaal,  85 
Trent  river,  27 
tributary,  53,  61 
Tuolumne  river,  48 

Undermining;,  76 
upland,  19,  23,  53,  54 
uplift,  15,  41 
upwarp,  47 

Valley,  4,  7,  88-95 
consequent,  19 
drowned,  27,50,  97,108 
hanging,  4,  53,  58,  107, 
108 


valley,  insequent,  25 

longitudinal,  88,  93 

mature,  23,  26 

meandering,  43 

transverse,  93 

young,  23,112 
valley  system,  4 
Venezuela,  125 
Vesuvius,  75 
Victoria  falls,  33 
volcanoes,  66-79 

dissected,  70,  73,  75 

Warm  wave,  135 

warping:,  47,  50,  64,  81,  87 

waste,  6,  31,  58,  61,  85, 
100,  104 

waterfalls.    See  Falls 

water  gap,  92 

waves,  107,  108,  110 

weather,  123,  129-137 

weather  maps,  129-237 

weather  elements,  129 

weathering,  6,  31,  107 

West  Virginia,  44 

westerly  winds,  122-127, 
136 

Wicomico  river,  28 

wind  belt,  122 

wind  gap,  92 

winds,  121-128,  129-137 
backing,  134,  136 
trade,  122-127 
veering,  134,  136 
•westerly,  122-1'?" 

windward,  121 

winter,  118,  123 

Zambezi  river,  33,  125 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


Form  L9-100m-9,'52(A3105)444 


LOS 


!SSLSf§9?!*t  LIBRARY  FACILITY 


A     000  582  723     3 


i:  i 


-  vurORNU 

S.  CAUK, 


